Methods and compositions for diagnosis and prognosis of renal injury and renal failure

ABSTRACT

The present invention relates to methods and compositions for monitoring, diagnosis, prognosis, and determination of treatment regimens in subjects suffering from or suspected of having a renal injury. In particular, the invention relates to using a one or more assays configured to detect a kidney injury marker selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 as diagnostic and prognostic biomarkers in renal injuries.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is filed under 35 U.S.C. § 371 as the U.S. national phase of International Application No. PCT/US2010/055730, filed Nov. 5, 2010, which designated the U.S. and claims the benefit of priority to U.S. Provisional Patent Application No. 61/259,163 filed Nov. 7, 2009; U.S. Provisional Patent Application No. 61/259,540filed Nov. 9, 2009; U.S. Provisional Patent Application No. 61/259,140 filed Nov. 7, 2009; U.S. Provisional Patent Application No. 61/259,142 filed Nov. 7, 2009; U.S. Provisional Patent Application No. 61/259,143 filed Nov. 7, 2009; U.S. Provisional Patent Application No. 61/259,141 filed Nov. 7, 2009; and U.S. Provisional Patent Application No. 61/259,511 filed Nov. 9, 2009, each of which is hereby incorporated in its entirety including all tables, figures, and claims.

SEQUENCE LISTING

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BACKGROUND OF THE INVENTION

The following discussion of the background of the invention is merely provided to aid the reader in understanding the invention and is not admitted to describe or constitute prior art to the present invention.

The kidney is responsible for water and solute excretion from the body. Its functions include maintenance of acid-base balance, regulation of electrolyte concentrations, control of blood volume, and regulation of blood pressure. As such, loss of kidney function through injury and/or disease results in substantial morbidity and mortality. A detailed discussion of renal injuries is provided in Harrison's Principles of Internal Medicine, 17^(th) Ed., McGraw Hill, New York, pages 1741-1830, which are hereby incorporated by reference in their entirety. Renal disease and/or injury may be acute or chronic. Acute and chronic kidney disease are described as follows (from Current Medical Diagnosis & Treatment 2008, 47^(th) Ed, McGraw Hill, New York, pages 785-815, which are hereby incorporated by reference in their entirety): “Acute renal failure is worsening of renal function over hours to days, resulting in the retention of nitrogenous wastes (such as urea nitrogen) and creatinine in the blood. Retention of these substances is called azotemia. Chronic renal failure (chronic kidney disease) results from an abnormal loss of renal function over months to years”.

Acute renal failure (ARF, also known as acute kidney injury, or AKI) is an abrupt (typically detected within about 48 hours to 1 week) reduction in glomerular filtration. This loss of filtration capacity results in retention of nitrogenous (urea and creatinine) and non-nitrogenous waste products that are normally excreted by the kidney, a reduction in urine output, or both. It is reported that ARF complicates about 5% of hospital admissions, 4-15% of cardiopulmonary bypass surgeries, and up to 30% of intensive care admissions. ARF may be categorized as prerenal, intrinsic renal, or postrenal in causation. Intrinsic renal disease can be further divided into glomerular, tubular, interstitial, and vascular abnormalities. Major causes of ARF are described in the following table, which is adapted from the Merck Manual, 17^(th) ed., Chapter 222, and which is hereby incorporated by reference in their entirety:

Type Risk Factors Prerenal ECF volume depletion Excessive diuresis, hemorrhage, GI losses, loss of intravascular fluid into the extravascular space (due to ascites, peritonitis, pancreatitis, or burns), loss of skin and mucus membranes, renal salt- and water-wasting states Low cardiac output Cardiomyopathy, MI, cardiac tamponade, pulmonary embolism, pulmonary hypertension, positive-pressure mechanical ventilation Low systemic vascular Septic shock, liver failure, antihypertensive drugs resistance Increased renal vascular NSAIDs, cyclosporines, tacrolimus, hypercalcemia, resistance anaphylaxis, anesthetics, renal artery obstruction, renal vein thrombosis, sepsis, hepatorenal syndrome Decreased efferent ACE inhibitors or angiotensin II receptor blockers arteriolar tone (leading to decreased GFR from reduced glomerular transcapillary pressure, especially in patients with bilateral renal artery stenosis) Intrinsic Renal Acute tubular injury Ischemia (prolonged or severe prerenal state): surgery, hemorrhage, arterial or venous obstruction; Toxins: NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, streptozotocin Acute glomerulonephritis ANCA-associated: Crescentic glomerulonephritis, polyarteritis nodosa, Wegener's granulomatosis; Anti- GBM glomerulonephritis: Goodpasture's syndrome; Immune-complex: Lupus glomerulonephritis, postinfectious glomerulonephritis, cryoglobulinemic glomerulonephritis Acute tubulointerstitial Drug reaction (eg, β-lactams, NSAIDs, sulfonamides, nephritis ciprofloxacin, thiazide diuretics, furosemide, phenytoin, allopurinol, pyelonephritis, papillary necrosis Acute vascular Vasculitis, malignant hypertension, thrombotic nephropathy microangiopathies, scleroderma, atheroembolism Infiltrative diseases Lymphoma, sarcoidosis, leukemia Postrenal Tubular precipitation Uric acid (tumor lysis), sulfonamides, triamterene, acyclovir, indinavir, methotrexate, ethylene glycol ingestion, myeloma protein, myoglobin Ureteral obstruction Intrinsic: Calculi, clots, sloughed renal tissue, fungus ball, edema, malignancy, congenital defects; Extrinsic: Malignancy, retroperitoneal fibrosis, ureteral trauma during surgery or high impact injury Bladder obstruction Mechanical: Benign prostatic hyperplasia, prostate cancer, bladder cancer, urethral strictures, phimosis, paraphimosis, urethral valves, obstructed indwelling urinary catheter; Neurogenic: Anticholinergic drugs, upper or lower motor neuron lesion

In the case of ischemic ARF, the course of the disease may be divided into four phases. During an initiation phase, which lasts hours to days, reduced perfusion of the kidney is evolving into injury. Glomerular ultrafiltration reduces, the flow of filtrate is reduced due to debris within the tubules, and back leakage of filtrate through injured epithelium occurs. Renal injury can be mediated during this phase by reperfusion of the kidney. Initiation is followed by an extension phase which is characterized by continued ischemic injury and inflammation and may involve endothelial damage and vascular congestion. During the maintenance phase, lasting from 1 to 2 weeks, renal cell injury occurs, and glomerular filtration and urine output reaches a minimum. A recovery phase can follow in which the renal epithelium is repaired and GFR gradually recovers. Despite this, the survival rate of subjects with ARF may be as low as about 60%.

Acute kidney injury caused by radiocontrast agents (also called contrast media) and other nephrotoxins such as cyclosporine, antibiotics including aminoglycosides and anticancer drugs such as cisplatin manifests over a period of days to about a week. Contrast induced nephropathy (CIN, which is AKI caused by radiocontrast agents) is thought to be caused by intrarenal vasoconstriction (leading to ischemic injury) and from the generation of reactive oxygen species that are directly toxic to renal tubular epithelial cells. CIN classically presents as an acute (onset within 24-48 h) but reversible (peak 3-5 days, resolution within 1 week) rise in blood urea nitrogen and serum creatinine.

A commonly reported criteria for defining and detecting AKI is an abrupt (typically within about 2-7 days or within a period of hospitalization) elevation of serum creatinine. Although the use of serum creatinine elevation to define and detect AKI is well established, the magnitude of the serum creatinine elevation and the time over which it is measured to define AKI varies considerably among publications. Traditionally, relatively large increases in serum creatinine such as 100%, 200%, an increase of at least 100% to a value over 2 mg/dL and other definitions were used to define AKI. However, the recent trend has been towards using smaller serum creatinine rises to define AKI. The relationship between serum creatinine rise, AKI and the associated health risks are reviewed in Praught and Shlipak, Curr Opin Nephrol Hypertens 14:265-270, 2005 and Chertow et al, J Am Soc Nephrol 16: 3365-3370, 2005, which, with the references listed therein, are hereby incorporated by reference in their entirety. As described in these publications, acute worsening renal function (AKI) and increased risk of death and other detrimental outcomes are now known to be associated with very small increases in serum creatinine. These increases may be determined as a relative (percent) value or a nominal value. Relative increases in serum creatinine as small as 20% from the pre-injury value have been reported to indicate acutely worsening renal function (AKI) and increased health risk, but the more commonly reported value to define AKI and increased health risk is a relative increase of at least 25%. Nominal increases as small as 0.3 mg/dL, 0.2 mg/dL or even 0.1 mg/dL have been reported to indicate worsening renal function and increased risk of death. Various time periods for the serum creatinine to rise to these threshold values have been used to define AKI, for example, ranging from 2 days, 3 days, 7 days, or a variable period defined as the time the patient is in the hospital or intensive care unit. These studies indicate there is not a particular threshold serum creatinine rise (or time period for the rise) for worsening renal function or AKI, but rather a continuous increase in risk with increasing magnitude of serum creatinine rise.

One study (Lassnigg et all, J Am Soc Nephrol 15:1597-1605, 2004, hereby incorporated by reference in its entirety) investigated both increases and decreases in serum creatinine. Patients with a mild fall in serum creatinine of −0.1 to −0.3 mg/dL following heart surgery had the lowest mortality rate. Patients with a larger fall in serum creatinine (more than or equal to −0.4 mg/dL) or any increase in serum creatinine had a larger mortality rate. These findings caused the authors to conclude that even very subtle changes in renal function (as detected by small creatinine changes within 48 hours of surgery) seriously effect patient's outcomes. In an effort to reach consensus on a unified classification system for using serum creatinine to define AKI in clinical trials and in clinical practice, Bellomo et al., Crit. Care. 8(4):R204-12, 2004, which is hereby incorporated by reference in its entirety, proposes the following classifications for stratifying AKI patients:

-   “Risk”: serum creatinine increased 1.5 fold from baseline OR urine     production of <0.5 ml/kg body weight/hr for 6 hours; -   “Injury”: serum creatinine increased 2.0 fold from baseline OR urine     production <0.5 ml/kg/hr for 12 h; -   “Failure”: serum creatinine increased 3.0 fold from baseline OR     creatinine >355 μmol/l (with a rise of >44) or urine output below     0.3 ml/kg/hr for 24 h or anuria for at least 12 hours;     And included two clinical outcomes: -   “Loss”: persistent need for renal replacement therapy for more than     four weeks. -   “ESRD”: end stage renal disease—the need for dialysis for more than     3 months.

These criteria are called the RIFLE criteria, which provide a useful clinical tool to classify renal status. As discussed in Kellum, Crit. Care Med. 36: S141-45, 2008 and Ricci et al., Kidney Int. 73, 538-546, 2008, each hereby incorporated by reference in its entirety, the RIFLE criteria provide a uniform definition of AKI which has been validated in numerous studies.

More recently, Mehta et al., Crit. Care 11:R31 (doi:10.1186.cc5713), 2007, hereby incorporated by reference in its entirety, proposes the following similar classifications for stratifying AKI patients, which have been modified from RIFLE:

-   “Stage I”: increase in serum creatinine of more than or equal to 0.3     mg/dL (≥26.4 μmol/L) or increase to more than or equal to 150%     (1.5-fold) from baseline OR urine output less than 0.5 mL/kg per     hour for more than 6 hours; -   “Stage II”: increase in serum creatinine to more than 200% (>2-fold)     from baseline OR urine output less than 0.5 mL/kg per hour for more     than 12 hours; -   “Stage III”: increase in serum creatinine to more than 300%     (>3-fold) from baseline OR serum creatinine ≥354 μmol/L accompanied     by an acute increase of at least 44 μmol/L OR urine output less than     0.3 mL/kg per hour for 24 hours or anuria for 12 hours.

The CIN Consensus Working Panel (McCollough et al, Rev Cardiovasc Med. 2006; 7(4): 177-197, hereby incorporated by reference in its entirety) uses a serum creatinine rise of 25% to define Contrast induced nephropathy (which is a type of AKI). Although various groups propose slightly different criteria for using serum creatinine to detect AKI, the consensus is that small changes in serum creatinine, such as 0.3 mg/dL or 25%, are sufficient to detect AKI (worsening renal function) and that the magnitude of the serum creatinine change is an indicator of the severity of the AKI and mortality risk.

Although serial measurement of serum creatinine over a period of days is an accepted method of detecting and diagnosing AKI and is considered one of the most important tools to evaluate AKI patients, serum creatinine is generally regarded to have several limitations in the diagnosis, assessment and monitoring of AKI patients. The time period for serum creatinine to rise to values (e.g., a 0.3 mg/dL or 25% rise) considered diagnostic for AKI can be 48 hours or longer depending on the definition used. Since cellular injury in AKI can occur over a period of hours, serum creatinine elevations detected at 48 hours or longer can be a late indicator of injury, and relying on serum creatinine can thus delay diagnosis of AKI. Furthermore, serum creatinine is not a good indicator of the exact kidney status and treatment needs during the most acute phases of AKI when kidney function is changing rapidly. Some patients with AKI will recover fully, some will need dialysis (either short term or long term) and some will have other detrimental outcomes including death, major adverse cardiac events and chronic kidney disease. Because serum creatinine is a marker of filtration rate, it does not differentiate between the causes of AKI (pre-renal, intrinsic renal, post-renal obstruction, atheroembolic, etc) or the category or location of injury in intrinsic renal disease (for example, tubular, glomerular or interstitial in origin). Urine output is similarly limited, Knowing these things can be of vital importance in managing and treating patients with AKI.

These limitations underscore the need for better methods to detect and assess AKI, particularly in the early and subclinical stages, but also in later stages when recovery and repair of the kidney can occur. Furthermore, there is a need to better identify patients who are at risk of having an AKI.

BRIEF SUMMARY OF THE INVENTION

It is an object of the invention to provide methods and compositions for evaluating renal function in a subject. As described herein, measurement of one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 (each referred to herein as a “kidney injury marker”) can be used for diagnosis, prognosis, risk stratification, staging, monitoring, categorizing and determination of further diagnosis and treatment regimens in subjects suffering or at risk of suffering from an injury to renal function, reduced renal function, and/or acute renal failure (also called acute kidney injury).

The kidney injury markers of the present invention may be used, individually or in panels comprising a plurality of kidney injury markers, for risk stratification (that is, to identify subjects at risk for a future injury to renal function, for future progression to reduced renal function, for future progression to ARF, for future improvement in renal function, etc.); for diagnosis of existing disease (that is, to identify subjects who have suffered an injury to renal function, who have progressed to reduced renal function, who have progressed to ARF, etc.); for monitoring for deterioration or improvement of renal function; and for predicting a future medical outcome, such as improved or worsening renal function, a decreased or increased mortality risk, a decreased or increased risk that a subject will require renal replacement therapy (i.e., hemodialysis, peritoneal dialysis, hemofiltration, and/or renal transplantation, a decreased or increased risk that a subject will recover from an injury to renal function, a decreased or increased risk that a subject will recover from ARF, a decreased or increased risk that a subject will progress to end stage renal disease, a decreased or increased risk that a subject will progress to chronic renal failure, a decreased or increased risk that a subject will suffer rejection of a transplanted kidney, etc.

In a first aspect, the present invention relates to methods for evaluating renal status in a subject. These methods comprise performing an assay method that is configured to detect one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 is/are then correlated to the renal status of the subject. This correlation to renal status may include correlating the assay result(s) to one or more of risk stratification, diagnosis, prognosis, staging, classifying and monitoring of the subject as described herein. Thus, the present invention utilizes one or more kidney injury markers of the present invention for the evaluation of renal injury.

In certain embodiments, the methods for evaluating renal status described herein are methods for risk stratification of the subject; that is, assigning a likelihood of one or more future changes in renal status to the subject. In these embodiments, the assay result(s) is/are correlated to one or more such future changes. The following are preferred risk stratification embodiments.

In preferred risk stratification embodiments, these methods comprise determining a subject's risk for a future injury to renal function, and the assay result(s) is/are correlated to a likelihood of such a future injury to renal function. For example, the measured concentration(s) may each be compared to a threshold value. For a “positive going” kidney injury marker, an increased likelihood of suffering a future injury to renal function is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a “negative going” kidney injury marker, an increased likelihood of suffering a future injury to renal function is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.

In other preferred risk stratification embodiments, these methods comprise determining a subject's risk for future reduced renal function, and the assay result(s) is/are correlated to a likelihood of such reduced renal function. For example, the measured concentrations may each be compared to a threshold value. For a “positive going” kidney injury marker, an increased likelihood of suffering a future reduced renal function is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a “negative going” kidney injury marker, an increased likelihood of future reduced renal function is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.

In still other preferred risk stratification embodiments, these methods comprise determining a subject's likelihood for a future improvement in renal function, and the assay result(s) is/are correlated to a likelihood of such a future improvement in renal function. For example, the measured concentration(s) may each be compared to a threshold value. For a “positive going” kidney injury marker, an increased likelihood of a future improvement in renal function is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold. For a “negative going” kidney injury marker, an increased likelihood of a future improvement in renal function is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold.

In yet other preferred risk stratification embodiments, these methods comprise determining a subject's risk for progression to ARF, and the result(s) is/are correlated to a likelihood of such progression to ARF. For example, the measured concentration(s) may each be compared to a threshold value. For a “positive going” kidney injury marker, an increased likelihood of progression to ARF is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a “negative going” kidney injury marker, an increased likelihood of progression to ARF is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.

And in other preferred risk stratification embodiments, these methods comprise determining a subject's outcome risk, and the assay result(s) is/are correlated to a likelihood of the occurrence of a clinical outcome related to a renal injury suffered by the subject. For example, the measured concentration(s) may each be compared to a threshold value. For a “positive going” kidney injury marker, an increased likelihood of one or more of: acute kidney injury, progression to a worsening stage of AKI, mortality, a requirement for renal replacement therapy, a requirement for withdrawal of renal toxins, end stage renal disease, heart failure, stroke, myocardial infarction, progression to chronic kidney disease, etc., is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a “negative going” kidney injury marker, an increased likelihood of one or more of: acute kidney injury, progression to a worsening stage of AKI, mortality, a requirement for renal replacement therapy, a requirement for withdrawal of renal toxins, end stage renal disease, heart failure, stroke, myocardial infarction, progression to chronic kidney disease, etc., is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.

In such risk stratification embodiments, preferably the likelihood or risk assigned is that an event of interest is more or less likely to occur within 180 days of the time at which the body fluid sample is obtained from the subject. In particularly preferred embodiments, the likelihood or risk assigned relates to an event of interest occurring within a shorter time period such as 18 months, 120 days, 90 days, 60 days, 45 days, 30 days, 21 days, 14 days, 7 days, 5 days, 96 hours, 72 hours, 48 hours, 36 hours, 24 hours, 12 hours, or less. A risk at 0 hours of the time at which the body fluid sample is obtained from the subject is equivalent to diagnosis of a current condition.

In preferred risk stratification embodiments, the subject is selected for risk stratification based on the pre-existence in the subject of one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF. For example, a subject undergoing or having undergone major vascular surgery, coronary artery bypass, or other cardiac surgery; a subject having pre-existing congestive heart failure, preeclampsia, eclampsia, diabetes mellitus, hypertension, coronary artery disease, proteinuria, renal insufficiency, glomerular filtration below the normal range, cirrhosis, serum creatinine above the normal range, or sepsis; or a subject exposed to NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin are all preferred subjects for monitoring risks according to the methods described herein. This list is not meant to be limiting. By “pre-existence” in this context is meant that the risk factor exists at the time the body fluid sample is obtained from the subject. In particularly preferred embodiments, a subject is chosen for risk stratification based on an existing diagnosis of injury to renal function, reduced renal function, or ARF.

In other embodiments, the methods for evaluating renal status described herein are methods for diagnosing a renal injury in the subject; that is, assessing whether or not a subject has suffered from an injury to renal function, reduced renal function, or ARF. In these embodiments, the assay result(s), for example measured concentration(s) of one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 is/are correlated to the occurrence or nonoccurrence of a change in renal status. The following are preferred diagnostic embodiments.

In preferred diagnostic embodiments, these methods comprise diagnosing the occurrence or nonoccurrence of an injury to renal function, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of such an injury. For example, each of the measured concentration(s) may be compared to a threshold value. For a positive going marker, an increased likelihood of the occurrence of an injury to renal function is assigned to the subject when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, when the measured concentration is below the threshold, an increased likelihood of the nonoccurrence of an injury to renal function may be assigned to the subject (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the occurrence of an injury to renal function is assigned to the subject when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, when the measured concentration is above the threshold, an increased likelihood of the nonoccurrence of an injury to renal function may be assigned to the subject (relative to the likelihood assigned when the measured concentration is below the threshold).

In other preferred diagnostic embodiments, these methods comprise diagnosing the occurrence or nonoccurrence of reduced renal function, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of an injury causing reduced renal function. For example, each of the measured concentration(s) may be compared to a threshold value. For a positive going marker, an increased likelihood of the occurrence of an injury causing reduced renal function is assigned to the subject when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, when the measured concentration is below the threshold, an increased likelihood of the nonoccurrence of an injury causing reduced renal function may be assigned to the subject (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the occurrence of an injury causing reduced renal function is assigned to the subject when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, when the measured concentration is above the threshold, an increased likelihood of the nonoccurrence of an injury causing reduced renal function may be assigned to the subject (relative to the likelihood assigned when the measured concentration is below the threshold).

In yet other preferred diagnostic embodiments, these methods comprise diagnosing the occurrence or nonoccurrence of ARF, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of an injury causing ARF. For example, each of the measured concentration(s) may be compared to a threshold value. For a positive going marker, an increased likelihood of the occurrence of ARF is assigned to the subject when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, when the measured concentration is below the threshold, an increased likelihood of the nonoccurrence of ARF may be assigned to the subject (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the occurrence of ARF is assigned to the subject when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, when the measured concentration is above the threshold, an increased likelihood of the nonoccurrence of ARF may be assigned to the subject (relative to the likelihood assigned when the measured concentration is below the threshold).

In still other preferred diagnostic embodiments, these methods comprise diagnosing a subject as being in need of renal replacement therapy, and the assay result(s) is/are correlated to a need for renal replacement therapy. For example, each of the measured concentration(s) may be compared to a threshold value. For a positive going marker, an increased likelihood of the occurrence of an injury creating a need for renal replacement therapy is assigned to the subject when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, when the measured concentration is below the threshold, an increased likelihood of the nonoccurrence of an injury creating a need for renal replacement therapy may be assigned to the subject (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the occurrence of an injury creating a need for renal replacement therapy is assigned to the subject when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, when the measured concentration is above the threshold, an increased likelihood of the nonoccurrence of an injury creating a need for renal replacement therapy may be assigned to the subject (relative to the likelihood assigned when the measured concentration is below the threshold).

In still other preferred diagnostic embodiments, these methods comprise diagnosing a subject as being in need of renal transplantation, and the assay result(s0 is/are correlated to a need for renal transplantation. For example, each of the measured concentration(s) may be compared to a threshold value. For a positive going marker, an increased likelihood of the occurrence of an injury creating a need for renal transplantation is assigned to the subject when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, when the measured concentration is below the threshold, an increased likelihood of the nonoccurrence of an injury creating a need for renal transplantation may be assigned to the subject (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the occurrence of an injury creating a need for renal transplantation is assigned to the subject when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, when the measured concentration is above the threshold, an increased likelihood of the nonoccurrence of an injury creating a need for renal transplantation may be assigned to the subject (relative to the likelihood assigned when the measured concentration is below the threshold).

In still other embodiments, the methods for evaluating renal status described herein are methods for monitoring a renal injury in the subject; that is, assessing whether or not renal function is improving or worsening in a subject who has suffered from an injury to renal function, reduced renal function, or ARF. In these embodiments, the assay result(s), for example measured concentration(s) of one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 is/are correlated to the occurrence or nonoccurrence of a change in renal status. The following are preferred monitoring embodiments.

In preferred monitoring embodiments, these methods comprise monitoring renal status in a subject suffering from an injury to renal function, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of a change in renal status in the subject. For example, the measured concentration(s) may be compared to a threshold value. For a positive going marker, when the measured concentration is above the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is below the threshold, an improvement of renal function may be assigned to the subject. For a negative going marker, when the measured concentration is below the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is above the threshold, an improvement of renal function may be assigned to the subject.

In other preferred monitoring embodiments, these methods comprise monitoring renal status in a subject suffering from reduced renal function, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of a change in renal status in the subject. For example, the measured concentration(s) may be compared to a threshold value. For a positive going marker, when the measured concentration is above the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is below the threshold, an improvement of renal function may be assigned to the subject. For a negative going marker, when the measured concentration is below the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is above the threshold, an improvement of renal function may be assigned to the subject.

In yet other preferred monitoring embodiments, these methods comprise monitoring renal status in a subject suffering from acute renal failure, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of a change in renal status in the subject. For example, the measured concentration(s) may be compared to a threshold value. For a positive going marker, when the measured concentration is above the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is below the threshold, an improvement of renal function may be assigned to the subject. For a negative going marker, when the measured concentration is below the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is above the threshold, an improvement of renal function may be assigned to the subject.

In other additional preferred monitoring embodiments, these methods comprise monitoring renal status in a subject at risk of an injury to renal function due to the pre-existence of one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF, and the assay result(s) is/are correlated to the occurrence or nonoccurrence of a change in renal status in the subject. For example, the measured concentration(s) may be compared to a threshold value. For a positive going marker, when the measured concentration is above the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is below the threshold, an improvement of renal function may be assigned to the subject. For a negative going marker, when the measured concentration is below the threshold, a worsening of renal function may be assigned to the subject; alternatively, when the measured concentration is above the threshold, an improvement of renal function may be assigned to the subject.

In still other embodiments, the methods for evaluating renal status described herein are methods for classifying a renal injury in the subject; that is, determining whether a renal injury in a subject is prerenal, intrinsic renal, or postrenal; and/or further subdividing these classes into subclasses such as acute tubular injury, acute glomerulonephritis acute tubulointerstitial nephritis, acute vascular nephropathy, or infiltrative disease; and/or assigning a likelihood that a subject will progress to a particular RIFLE stage. In these embodiments, the assay result(s), for example measured concentration(s) of one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 is/are correlated to a particular class and/or subclass. The following are preferred classification embodiments.

In preferred classification embodiments, these methods comprise determining whether a renal injury in a subject is prerenal, intrinsic renal, or postrenal; and/or further subdividing these classes into subclasses such as acute tubular injury, acute glomerulonephritis acute tubulointerstitial nephritis, acute vascular nephropathy, or infiltrative disease; and/or assigning a likelihood that a subject will progress to a particular RIFLE stage, and the assay result(s) is/are correlated to the injury classification for the subject. For example, the measured concentration may be compared to a threshold value, and when the measured concentration is above the threshold, a particular classification is assigned; alternatively, when the measured concentration is below the threshold, a different classification may be assigned to the subject.

A variety of methods may be used by the skilled artisan to arrive at a desired threshold value for use in these methods. For example, the threshold value may be determined from a population of normal subjects by selecting a concentration representing the 75^(th), 85^(th), 90^(th), 95^(th), or 99^(th) percentile of a kidney injury marker measured in such normal subjects. Alternatively, the threshold value may be determined from a “diseased” population of subjects, e.g., those suffering from an injury or having a predisposition for an injury (e.g., progression to ARF or some other clinical outcome such as death, dialysis, renal transplantation, etc.), by selecting a concentration representing the 75^(th), 85^(th), 90^(th), 95^(th), or 99^(th) percentile of a kidney injury marker measured in such subjects. In another alternative, the threshold value may be determined from a prior measurement of a kidney injury marker in the same subject; that is, a temporal change in the level of a kidney injury marker in the subject may be used to assign risk to the subject.

The foregoing discussion is not meant to imply, however, that the kidney injury markers of the present invention must be compared to corresponding individual thresholds. Methods for combining assay results can comprise the use of multivariate logistical regression, loglinear modeling, neural network analysis, n-of-m analysis, decision tree analysis, calculating ratios of markers, etc. This list is not meant to be limiting. In these methods, a composite result which is determined by combining individual markers may be treated as if it is itself a marker; that is, a threshold may be determined for the composite result as described herein for individual markers, and the composite result for an individual patient compared to this threshold.

The ability of a particular test to distinguish two populations can be established using ROC analysis. For example, ROC curves established from a “first” subpopulation which is predisposed to one or more future changes in renal status, and a “second” subpopulation which is not so predisposed can be used to calculate a ROC curve, and the area under the curve provides a measure of the quality of the test. Preferably, the tests described herein provide a ROC curve area greater than 0.5, preferably at least 0.6, more preferably 0.7, still more preferably at least 0.8, even more preferably at least 0.9, and most preferably at least 0.95.

In certain aspects, the measured concentration of one or more kidney injury markers, or a composite of such markers, may be treated as continuous variables. For example, any particular concentration can be converted into a corresponding probability of a future reduction in renal function for the subject, the occurrence of an injury, a classification, etc. In yet another alternative, a threshold that can provide an acceptable level of specificity and sensitivity in separating a population of subjects into “bins” such as a “first” subpopulation (e.g., which is predisposed to one or more future changes in renal status, the occurrence of an injury, a classification, etc.) and a “second” subpopulation which is not so predisposed. A threshold value is selected to separate this first and second population by one or more of the following measures of test accuracy:

-   an odds ratio greater than 1, preferably at least about 2 or more or     about 0.5 or less, more preferably at least about 3 or more or about     0.33 or less, still more preferably at least about 4 or more or     about 0.25 or less, even more preferably at least about 5 or more or     about 0.2 or less, and most preferably at least about 10 or more or     about 0.1 or less; -   a specificity of greater than 0.5, preferably at least about 0.6,     more preferably at least about 0.7, still more preferably at least     about 0.8, even more preferably at least about 0.9 and most     preferably at least about 0.95, with a corresponding sensitivity     greater than 0.2, preferably greater than about 0.3, more preferably     greater than about 0.4, still more preferably at least about 0.5,     even more preferably about 0.6, yet more preferably greater than     about 0.7, still more preferably greater than about 0.8, more     preferably greater than about 0.9, and most preferably greater than     about 0.95; -   a sensitivity of greater than 0.5, preferably at least about 0.6,     more preferably at least about 0.7, still more preferably at least     about 0.8, even more preferably at least about 0.9 and most     preferably at least about 0.95, with a corresponding specificity     greater than 0.2, preferably greater than about 0.3, more preferably     greater than about 0.4, still more preferably at least about 0.5,     even more preferably about 0.6, yet more preferably greater than     about 0.7, still more preferably greater than about 0.8, more     preferably greater than about 0.9, and most preferably greater than     about 0.95; -   at least about 75% sensitivity, combined with at least about 75%     specificity; -   a positive likelihood ratio (calculated as     sensitivity/(1-specificity)) of greater than 1, at least about 2,     more preferably at least about 3, still more preferably at least     about 5, and most preferably at least about 10; or -   a negative likelihood ratio (calculated as     (1-sensitivity)/specificity) of less than 1, less than or equal to     about 0.5, more preferably less than or equal to about 0.3, and most     preferably less than or equal to about 0.1.

The term “about” in the context of any of the above measurements refers to +/−5% of a given measurement.

Multiple thresholds may also be used to assess renal status in a subject. For example, a “first” subpopulation which is predisposed to one or more future changes in renal status, the occurrence of an injury, a classification, etc., and a “second” subpopulation which is not so predisposed can be combined into a single group. This group is then subdivided into three or more equal parts (known as tertiles, quartiles, quintiles, etc., depending on the number of subdivisions). An odds ratio is assigned to subjects based on which subdivision they fall into. If one considers a tertile, the lowest or highest tertile can be used as a reference for comparison of the other subdivisions. This reference subdivision is assigned an odds ratio of 1. The second tertile is assigned an odds ratio that is relative to that first tertile. That is, someone in the second tertile might be 3 times more likely to suffer one or more future changes in renal status in comparison to someone in the first tertile. The third tertile is also assigned an odds ratio that is relative to that first tertile.

In certain embodiments, the assay method is an immunoassay. Antibodies for use in such assays will specifically bind a full length kidney injury marker of interest, and may also bind one or more polypeptides that are “related” thereto, as that term is defined hereinafter. Numerous immunoassay formats are known to those of skill in the art. Preferred body fluid samples are selected from the group consisting of urine, blood, serum, saliva, tears, and plasma.

The foregoing method steps should not be interpreted to mean that the kidney injury marker assay result(s) is/are used in isolation in the methods described herein. Rather, additional variables or other clinical indicia may be included in the methods described herein. For example, a risk stratification, diagnostic, classification, monitoring, etc. method may combine the assay result(s) with one or more variables measured for the subject selected from the group consisting of demographic information (e.g., weight, sex, age, race), medical history (e.g., family history, type of surgery, pre-existing disease such as aneurism, congestive heart failure, preeclampsia, eclampsia, diabetes mellitus, hypertension, coronary artery disease, proteinuria, renal insufficiency, or sepsis, type of toxin exposure such as NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin), clinical variables (e.g., blood pressure, temperature, respiration rate), risk scores (APACHE score, PREDICT score, TIMI Risk Score for UA/NSTEMI, Framingham Risk Score), a glomerular filtration rate, an estimated glomerular filtration rate, a urine production rate, a serum or plasma creatinine concentration, a urine creatinine concentration, a fractional excretion of sodium, a urine sodium concentration, a urine creatinine to serum or plasma creatinine ratio, a urine specific gravity, a urine osmolality, a urine urea nitrogen to plasma urea nitrogen ratio, a plasma BUN to creatnine ratio, a renal failure index calculated as urine sodium/(urine creatinine/plasma creatinine), a serum or plasma neutrophil gelatinase (NGAL) concentration, a urine NGAL concentration, a serum or plasma cystatin C concentration, a serum or plasma cardiac troponin concentration, a serum or plasma BNP concentration, a serum or plasma NTproBNP concentration, and a serum or plasma proBNP concentration. Other measures of renal function which may be combined with one or more kidney injury marker assay result(s) are described hereinafter and in Harrison's Principles of Internal Medicine, 17^(th) Ed., McGraw Hill, New York, pages 1741-1830, and Current Medical Diagnosis & Treatment 2008, 47^(th) Ed, McGraw Hill, New York, pages 785-815, each of which are hereby incorporated by reference in their entirety.

When more than one marker is measured, the individual markers may be measured in samples obtained at the same time, or may be determined from samples obtained at different (e.g., an earlier or later) times. The individual markers may also be measured on the same or different body fluid samples. For example, one kidney injury marker may be measured in a serum or plasma sample and another kidney injury marker may be measured in a urine sample. In addition, assignment of a likelihood may combine an individual kidney injury marker assay result with temporal changes in one or more additional variables.

In various related aspects, the present invention also relates to devices and kits for performing the methods described herein. Suitable kits comprise reagents sufficient for performing an assay for at least one of the described kidney injury markers, together with instructions for performing the described threshold comparisons.

In certain embodiments, reagents for performing such assays are provided in an assay device, and such assay devices may be included in such a kit. Preferred reagents can comprise one or more solid phase antibodies, the solid phase antibody comprising antibody that detects the intended biomarker target(s) bound to a solid support. In the case of sandwich immunoassays, such reagents can also include one or more detectably labeled antibodies, the detectably labeled antibody comprising antibody that detects the intended biomarker target(s) bound to a detectable label. Additional optional elements that may be provided as part of an assay device are described hereinafter.

Detectable labels may include molecules that are themselves detectable (e.g., fluorescent moieties, electrochemical labels, ecl (electrochemical luminescence) labels, metal chelates, colloidal metal particles, etc.) as well as molecules that may be indirectly detected by production of a detectable reaction product (e.g., enzymes such as horseradish peroxidase, alkaline phosphatase, etc.) or through the use of a specific binding molecule which itself may be detectable (e.g., a labeled antibody that binds to the second antibody, biotin, digoxigenin, maltose, oligohistidine, 2,4-dintrobenzene, phenylarsenate, ssDNA, dsDNA, etc.).

Generation of a signal from the signal development element can be performed using various optical, acoustical, and electrochemical methods well known in the art. Examples of detection modes include fluorescence, radiochemical detection, reflectance, absorbance, amperometry, conductance, impedance, interferometry, ellipsometry, etc. In certain of these methods, the solid phase antibody is coupled to a transducer (e.g., a diffraction grating, electrochemical sensor, etc) for generation of a signal, while in others, a signal is generated by a transducer that is spatially separate from the solid phase antibody (e.g., a fluorometer that employs an excitation light source and an optical detector). This list is not meant to be limiting. Antibody-based biosensors may also be employed to determine the presence or amount of analytes that optionally eliminate the need for a labeled molecule.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to methods and compositions for diagnosis, differential diagnosis, risk stratification, monitoring, classifying and determination of treatment regimens in subjects suffering or at risk of suffering from injury to renal function, reduced renal function and/or acute renal failure through measurement of one or more kidney injury markers. In various embodiments, a measured concentration of one or more biomarkers selected from the group consisting of Cathepsin B, Renin, Dipeptidyl Peptidase IV, Neprilysin, Beta-2-microglobulin, Carbonic anhydrase IX, and C-X-C motif chemokine 2 or one or more markers related thereto, are correlated to the renal status of the subject.

For purposes of this document, the following definitions apply:

As used herein, an “injury to renal function” is an abrupt (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) measurable reduction in a measure of renal function. Such an injury may be identified, for example, by a decrease in glomerular filtration rate or estimated GFR, a reduction in urine output, an increase in serum creatinine, an increase in serum cystatin C, a requirement for renal replacement therapy, etc. “Improvement in Renal Function” is an abrupt (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) measurable increase in a measure of renal function. Preferred methods for measuring and/or estimating GFR are described hereinafter.

As used herein, “reduced renal function” is an abrupt (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) reduction in kidney function identified by an absolute increase in serum creatinine of greater than or equal to 0.1 mg/dL (≥8.8 μmol/L), a percentage increase in serum creatinine of greater than or equal to 20% (1.2-fold from baseline), or a reduction in urine output (documented oliguria of less than 0.5 ml/kg per hour).

As used herein, “acute renal failure” or “ARF” is an abrupt (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) reduction in kidney function identified by an absolute increase in serum creatinine of greater than or equal to 0.3 mg/dl (≥26.4 μmol/l), a percentage increase in serum creatinine of greater than or equal to 50% (1.5-fold from baseline), or a reduction in urine output (documented oliguria of less than 0.5 ml/kg per hour for at least 6 hours). This term is synonymous with “acute kidney injury” or “AKI.”

As used herein, the term “Cathepsin B” refers to one or more polypeptides present in a biological sample that are derived from the Cathepsin B precursor (Swiss-Prot P07858 (SEQ ID NO: 1))

        10         20         30         40         50         60 MWQLWASLCC LLVLANARSR PSFHPLSDEL VNYVNKRNTT WQAGHNFYNV DMSYLKRLCG         70         80         90        100        110        120 TFLGGPKPPQ RVMFTEDLKL PASFDAREQW PQCPTIKEIR DQGSCGSCWA FGAVEAISDR        130        140        150        160        170        180 ICIHTNAHVS VEVSAEDLLT CCGSMCGDGC NGGYPAEAWN FWTRKGLVSG GLYESHVGCR        190        200        210        220        230        240 PYSIPPCEHH VNGSRPPCTG EGDTPKCSKI CEPGYSPTYK QDKHYGYNSY SVSNSEKDIM        250        260        270        280        290        300 AEIYKNGPVE GAFSVYSDFL LYKSGVYQHV TGEMMGGHAI RILGWGVENG TPYWLVANSW        310        320        330 NTDWGDNGFF KILRGQDHCG IESEVVAGIP RTDQYWEKI

The following domains have been identified in Cathepsin B:

Residues Length Domain ID  1-17 17 signal peptide 18-79 62 activation peptide 334-339 6 propeptide  80-333 254 Cathepsin B  80-126 47 Cathepsin B light chain 129-333 205 Cathepsin B heavy chain

As used herein, the term “Renin” refers to one or more polypeptides present in a biological sample that are derived from the Renin precursor (Swiss-Prot P00797 (SEQ ID NO: 2)).

        10         20         30         40         50         60 MDGWRRMPRW GLLLLLWGSC TFGLPTDTTT FKRIFLKRMP SIRESLKERG VDMARLGPEW         70         80         90        100        110        120 SQPMKRLTLG NTTSSVILTN YMDTQYYGEI GIGTPPQTFK VVFDTGSSNV WVPSSKCSRL        130        140        150        160        170        180 YTACVYHKLF DASDSSSYKH NGTELTLRYS TGTVSGFLSQ DIITVGGITV TQMFGEVTEM        190        200        210        220        230        240 PALPFMLAEF DGVVGMGFIE QAIGRVTPIF DNIISQGVLK EDVFSFYYNR DSENSQSLGG        250        260        270        280        290        300 QIVLGGSDPQ HYEGNFHYIN LIKTGVWQIQ MKGVSVGSST LLCEDGCLAL VDTGASYISG        310        320        330        340        350        360 STSSIEKLME ALGAKKRLFD YVVKCNEGPT LPDISFHLGG KEYTLTSADY VFQESYSSKK        370        380        390        400 LCTLAIHAMD IPPPTGPTWA LGATFIRKFY TEFDRRNNRI GFALAR

The following domains have been identified in Renin:

Residues Length Domain ID  1-23 23 Propeptide 24-66 43 Activation peptide  67-406 340 Renin 231-233 3 Missing in isoform 2

As used herein, the term “Dipeptidyl peptidase 4” refers to one or more polypeptides present in a biological sample that are derived from the Dipeptidyl peptidase 4 precursor (Swiss-Prot P27487 (SEQ ID NO: 3))

        10         20         30         40         50         60 MKTPWKVLLG LLGAAALVTI ITVPVVLLNK GTDDATADSR KTYTLTDYLK NTYRLKLYSL         70         80         90        100        110        120 RWISDHEYLY KQENNILVFN AEYGNSSVFL ENSTFDEFGH SINDYSISPD GQFILLEYNY        130        140        150        160        170        180 VKQWRHSYTA SYDIYDLNKR QLITEERIPN NTQWVTWSPV GHKLAYVWNN DIYVKIEPNL        190        200        210        220        230        240 PSYRITWTGK EDIIYNGITD WVYEEEVFSA YSALWWSPNG TFLAYAQFND TEVPLIEYSF        250        260        270        280        290        300 YSDESLQYPK TVRVPYPKAG AVNPTVKFFV VNTDSLSSVT NATSIQITAP ASMLIGDHYL        310        320        330        340        350        360 CDVTWATQER ISLQWLRRIQ NYSVMDICDY DESSGRWNCL VARQHIEMST TGWVGRFRPS        370        380        390        400        410        420 EPHFTLDGNS FYKIISNEEG YRHICYFQID KKDCTFITKG TWEVIGIEAL TSDYLYYISN        430        440        450        460        470        480 EYKGMPGGRN LYKIQLSDYT KVTCLSCELN PERCQYYSVS FSKEAKYYQL RCSGPGLPLY        490        500        510        520        530        540 TLHSSVNDKG LRVLEDNSAL DKMLQNVQMP SKKLDFIILN ETKFWYQMIL PPHFDKSKKY        550        560        570        580        590        600 PLLLDVYAGP CSQKADTVFR LNWATYLAST ENIIVASFDG RGSGYQGDKI MHAINRRLGT        610        620        630        640        650        660 FEVEDQIEAA RQFSKMGFVD NKRIAIWGWS YGGYVTSMVL GSGSGVFKCG IAVAPVSRWE        670        680        690        700        710        720 YYDSVYTERY MGLPTPEDNL DHYRNSTVMS RAENFKQVEY LLIHGTADDN VHFQQSAQIS        730        740        750        760 KALVDVGVDF QAMWYTDEDH GIASSTAHQH IYTHMSHFIK QCFSLP

Most preferably, the Dipeptidyl peptidase 4 assay detects one or more soluble forms of Dipeptidyl peptidase 4. Dipeptidyl peptidase 4 is a type II membrane protein having a large extracellular domain, most or all of which is present in soluble forms of Dipeptidyl peptidase 4 generated either through alternative splicing event which deletes all or a portion of the transmembrane domain, or by proteolysis of the membrane-bound form. In the case of an immunoassay, one or more antibodies that bind to epitopes within this extracellular domain may be used to detect these soluble form(s). The following domains have been identified in Dipeptidyl peptidase 4:

Residues Length Domain ID Residues Length Domain ID  1-766 766 Dipeptidyl peptidase 4 39-766 728 Dipeptidyl peptidase 4, soluble form 1-6  6 Cytoplasmic 7-28 22 Anchor signal 29-766 738 Extracellular

As used herein, the term “Neprilysin” refers to one or more polypeptides present in a biological sample that are derived from the Neprilysin precursor (Swiss-Prot P08473 (SEQ ID NO: 4))

       10          20         30         40         50         60 MGKSESQMDI TDINTPKPKK KQRWTPLEIS LSVLVLLLTI IAVTMIALYA TYDDGICKSS         70         80         90        100        110        120 DCIKSAARLI QNMDATTEPC TDFFKYACGG WLKRNVIPET SSRYGNFDIL RDELEVVLKD        130        140        150        160        170        180 VLQEPKTEDI VAVQKAKALY RSCINESAID SRGGEPLLKL LPDIYGWPVA TENWEQKYGA        190        200        210        220        230        240 SWTAEKAIAQ LNSKYGKKVL INLFVGTDDK NSVNHVIHID QPRLGLPSRD YYECTGIYKE        250        260        270        280        290        300 ACTAYVDFMI SVARLIRQEE RLPIDENQLA LEMNKVMELE KEIANATAKP EDRNDPMLLY        310        320        330        340        350        360 NKMTLAQIQN NFSLEINGKP FSWLNFTNEI MSTVNISITN EEDVVVYAPE YLTKLKPILT        370        380        390        400        410        420 KYSARDLQNL MSWRFIMDLV SSLSRTYKES RNAFRKALYG TTSETATWRR CANYVNGNME        430        440        450        460        470        480 NAVGRLYVEA AFAGESKHVV EDLIAQIREV FIQTLDDLTW MDAETKKRAE EKALAIKERI        490        500        510        520        530        540 GYPDDIVSND NKLNNEYLEL NYKEDEYFEN IIQNLKFSQS KQLKKLREKV DKDEWISGAA        550        560        570        580        590        600 VVNAFYSSGR NQIVFPAGIL QPPFFSAQQS NSLNYGGIGM VIGHEITHGF DDNGRNFNKD        610        620        630        640        650        660 GDLVDWWTQQ SASNFKEQSQ CMVYQYGNFS WDLAGGQHLN GINTLGENIA DNGGLGQAYR        670        680        690        700        710        720 AYQNYIKKNG EEKLLPGLDL NHKQLFFLNF AQVWCGTYRP EYAVNSIKTD VHSPGNFRII        730        740        750 GTLQNSAEFS EAFHCRKNSY MNPEKKCRVW

Most preferably, the Neprilysin assay detects one or more soluble forms of Neprilysin. Neprilysin is a type II membrane protein having a large extracellular domain, most or all of which is present in soluble forms of Neprilysin generated either through alternative splicing event which deletes all or a portion of the transmembrane domain, or by proteolysis of the membrane-bound form. In the case of an immunoassay, one or more antibodies that bind to epitopes within this extracellular domain may be used to detect these soluble form(s). The following domains have been identified in Neprilysin:

Residues Length Domain ID 1 1 initiator methionine  2-750 749 Neprilysin 2-28 27 Cytoplasmic 29-51  23 Anchor signal 52-750 699 Extracellular

As used herein, the term “Beta-2-microglobulin” refers to one or more polypeptides present in a biological sample that are derived from the Beta-2-microglobulin precursor (Swiss-Prot P61769 (SEQ ID NO: 5))

        10         20         30         40         50         60 MSRSVALAVL ALLSLSGLEA IQRTPKIQVY SRHPAENGKS NFLNCYVSGF HPSDIEVDLL         70         80         90        100        110 KNGERIEKVE HSDLSFSKDW SFYLLYYTEF TPTEKDEYAC RVNHVTLSQP KIVKWDRDM

The following domains have been identified in Beta-2-microglobulin:

Residues Length Domain ID 1-20 20 signal peptide 21-119 99 Beta-2-microglobulin 22-119 21 Beta-2-microglobulin form pI 5.3

As used herein, the term “Carbonic anhydrase IX” refers to one or more polypeptides present in a biological sample that are derived from the Carbonic anhydrase IX precursor (Swiss-Prot Q16790 (SEQ ID NO: 6))

        10         20         30         40         50         60 MAPLCPSPWL PLLIPAPAPG LTVQLLLSLL LLVPVHPQRL PRMQEDSPLG GGSSGEDDPL         70         80         90        100        110        120 GEEDLPSEED SPREEDPPGE EDLPGEEDLP GEEDLPEVKP KSEEEGSLKL EDLPTVEAPG        130        140        150        160        170        180 DPQEPQNNAH RDKEGDDQSH WRYGGDPPWP RVSPACAGRF QSPVDIRPQL AAFCPALRPL        190        200        210        220        230        240 ELLGFQLPPL PELRLRNNGH SVQLTLPPGL EMALGPGREY RALQLHLHWG AAGRPGSEHT        250        260        270        280        290        300 VEGHRFPAEI HVVHLSTAFA RVDEALGRPG GLAVLAAFLE EGPEENSAYE QLLSRLEEIA        310        320        330        340        350        360 EEGSETQVPG LDISALLPSD FSRYFQYEGS LTTPPCAQGV IWTVFNQTVM LSAKQLHTLS        370        380        390        400        410        420 DTLWGPGDSR LQLNFRATQP LNGRVIEASF PAGVDSSPRA AEPVQLNSCL AAGDILALVF        430        440        450 GLLFAVTSVA FLVQMRRQHR RGTKGGVSYR PAEVAETGA

Most preferably, the Carbonic anhydrase IX assay detects one or more soluble forms of Carbonic anhydrase IX. Carbonic anhydrase IX is a type I membrane protein having a large extracellular domain, most or all of which is present in soluble forms of Carbonic anhydrase IX generated either through alternative splicing event which deletes all or a portion of the transmembrane domain, or by proteolysis of the membrane-bound form. In the case of an immunoassay, one or more antibodies that bind to epitopes within this extracellular domain may be used to detect these soluble form(s). The following domains have been identified in Carbonic anhydrase IX:

Residues Length Domain ID 1-37 37 Signal peptide 38-459 422 Carbonic anhydrase IX 38-414 377 Extracellular 415-435  21 Transmembrane domain 436-459  699 Cytoplasmic

As used herein, the term “C-X-C motif chemokine 2” refers to one or more polypeptides present in a biological sample that are derived from the C-X-C motif chemokine 2 precursor (Swiss-Prot P19875 (SEQ ID NO: 7)).

        10         20         30         40         50         60 MARATLSAAP SNPRLLRVAL LLLLLVAASR RAAGAPLATE LRCQCLQTLQ GIHLKNIQSV         70         80         90        100 KVKSPGPHCA QTEVIATLKN GQKACLNPAS PMVKKIIEKM LKNGKSN

The following domains have been identified in C-X-C motif chemokine 2:

Residues Length Domain ID 1-34 34 Signal peptide 35-107 73 C-X-C motif chemokine 2 39-107 69 GRO-beta

As used herein, the term “relating a signal to the presence or amount” of an analyte reflects the following understanding. Assay signals are typically related to the presence or amount of an analyte through the use of a standard curve calculated using known concentrations of the analyte of interest. As the term is used herein, an assay is “configured to detect” an analyte if an assay can generate a detectable signal indicative of the presence or amount of a physiologically relevant concentration of the analyte. Because an antibody epitope is on the order of 8 amino acids, an immunoassay configured to detect a marker of interest will also detect polypeptides related to the marker sequence, so long as those polypeptides contain the epitope(s) necessary to bind to the antibody or antibodies used in the assay. The term “related marker” as used herein with regard to a biomarker such as one of the kidney injury markers described herein refers to one or more fragments, variants, etc., of a particular marker or its biosynthetic parent that may be detected as a surrogate for the marker itself or as independent biomarkers. The term also refers to one or more polypeptides present in a biological sample that are derived from the biomarker precursor complexed to additional species, such as binding proteins, receptors, heparin, lipids, sugars, etc.

In this regard, the skilled artisan will understand that the signals obtained from an immunoassay are a direct result of complexes formed between one or more antibodies and the target biomolecule (i.e., the analyte) and polypeptides containing the necessary epitope(s) to which the antibodies bind. While such assays may detect the full length biomarker and the assay result be expressed as a concentration of a biomarker of interest, the signal from the assay is actually a result of all such “immunoreactive” polypeptides present in the sample. Expression of biomarkers may also be determined by means other than immunoassays, including protein measurements (such as dot blots, western blots, chromatographic methods, mass spectrometry, etc.) and nucleic acid measurements (mRNA quatitation). This list is not meant to be limiting.

The term “positive going” marker as that term is used herein refer to a marker that is determined to be elevated in subjects suffering from a disease or condition, relative to subjects not suffering from that disease or condition. The term “negative going” marker as that term is used herein refer to a marker that is determined to be reduced in subjects suffering from a disease or condition, relative to subjects not suffering from that disease or condition.

The term “subject” as used herein refers to a human or non-human organism. Thus, the methods and compositions described herein are applicable to both human and veterinary disease. Further, while a subject is preferably a living organism, the invention described herein may be used in post-mortem analysis as well. Preferred subjects are humans, and most preferably “patients,” which as used herein refers to living humans that are receiving medical care for a disease or condition. This includes persons with no defined illness who are being investigated for signs of pathology.

Preferably, an analyte is measured in a sample. Such a sample may be obtained from a subject, or may be obtained from biological materials intended to be provided to the subject. For example, a sample may be obtained from a kidney being evaluated for possible transplantation into a subject, and an analyte measurement used to evaluate the kidney for preexisting damage. Preferred samples are body fluid samples.

The term “body fluid sample” as used herein refers to a sample of bodily fluid obtained for the purpose of diagnosis, prognosis, classification or evaluation of a subject of interest, such as a patient or transplant donor. In certain embodiments, such a sample may be obtained for the purpose of determining the outcome of an ongoing condition or the effect of a treatment regimen on a condition. Preferred body fluid samples include blood, serum, plasma, cerebrospinal fluid, urine, saliva, sputum, and pleural effusions. In addition, one of skill in the art would realize that certain body fluid samples would be more readily analyzed following a fractionation or purification procedure, for example, separation of whole blood into serum or plasma components.

The term “diagnosis” as used herein refers to methods by which the skilled artisan can estimate and/or determine the probability (“a likelihood”) of whether or not a patient is suffering from a given disease or condition. In the case of the present invention, “diagnosis” includes using the results of an assay, most preferably an immunoassay, for a kidney injury marker of the present invention, optionally together with other clinical characteristics, to arrive at a diagnosis (that is, the occurrence or nonoccurrence) of an acute renal injury or ARF for the subject from which a sample was obtained and assayed. That such a diagnosis is “determined” is not meant to imply that the diagnosis is 100% accurate. Many biomarkers are indicative of multiple conditions. The skilled clinician does not use biomarker results in an informational vacuum, but rather test results are used together with other clinical indicia to arrive at a diagnosis. Thus, a measured biomarker level on one side of a predetermined diagnostic threshold indicates a greater likelihood of the occurrence of disease in the subject relative to a measured level on the other side of the predetermined diagnostic threshold.

Similarly, a prognostic risk signals a probability (“a likelihood”) that a given course or outcome will occur. A level or a change in level of a prognostic indicator, which in turn is associated with an increased probability of morbidity (e.g., worsening renal function, future ARF, or death) is referred to as being “indicative of an increased likelihood” of an adverse outcome in a patient.

Marker Assays

In general, immunoassays involve contacting a sample containing or suspected of containing a biomarker of interest with at least one antibody that specifically binds to the biomarker. A signal is then generated indicative of the presence or amount of complexes formed by the binding of polypeptides in the sample to the antibody. The signal is then related to the presence or amount of the biomarker in the sample. Numerous methods and devices are well known to the skilled artisan for the detection and analysis of biomarkers. See, e.g., U.S. Pat. Nos. 6,143,576; 6,113,855; 6,019,944; 5,985,579; 5,947,124; 5,939,272; 5,922,615; 5,885,527; 5,851,776; 5,824,799; 5,679,526; 5,525,524; and 5,480,792, and The Immunoassay Handbook, David Wild, ed. Stockton Press, New York, 1994, each of which is hereby incorporated by reference in its entirety, including all tables, figures and claims.

The assay devices and methods known in the art can utilize labeled molecules in various sandwich, competitive, or non-competitive assay formats, to generate a signal that is related to the presence or amount of the biomarker of interest. Suitable assay formats also include chromatographic, mass spectrographic, and protein “blotting” methods. Additionally, certain methods and devices, such as biosensors and optical immunoassays, may be employed to determine the presence or amount of analytes without the need for a labeled molecule. See, e.g., U.S. Pat. Nos. 5,631,171; and 5,955,377, each of which is hereby incorporated by reference in its entirety, including all tables, figures and claims. One skilled in the art also recognizes that robotic instrumentation including but not limited to Beckman ACCESS®, Abbott AXSYM®, Roche ELECSYS®, Dade Behring STRATUS® systems are among the immunoassay analyzers that are capable of performing immunoassays. But any suitable immunoassay may be utilized, for example, enzyme-linked immunoassays (ELISA), radioimmunoassays (RIAs), competitive binding assays, and the like.

Antibodies or other polypeptides may be immobilized onto a variety of solid supports for use in assays. Solid phases that may be used to immobilize specific binding members include include those developed and/or used as solid phases in solid phase binding assays. Examples of suitable solid phases include membrane filters, cellulose-based papers, beads (including polymeric, latex and paramagnetic particles), glass, silicon wafers, microparticles, nanoparticles, TentaGel™ resins (Rapp Polymere GmbH), AgroGel™ resins (I.L.S.A. Industria Lavorazione Sottoprodotti Animali S.P.A.), polyethylene glycol and acrylamide (PEGA) gels, SPOCC gels, and multiple-well plates. An assay strip could be prepared by coating the antibody or a plurality of antibodies in an array on solid support. This strip could then be dipped into the test sample and then processed quickly through washes and detection steps to generate a measurable signal, such as a colored spot. Antibodies or other polypeptides may be bound to specific zones of assay devices either by conjugating directly to an assay device surface, or by indirect binding. In an example of the later case, antibodies or other polypeptides may be immobilized on particles or other solid supports, and that solid support immobilized to the device surface.

Biological assays require methods for detection, and one of the most common methods for quantitation of results is to conjugate a detectable label to a protein or nucleic acid that has affinity for one of the components in the biological system being studied. Detectable labels may include molecules that are themselves detectable (e.g., fluorescent moieties, electrochemical labels, metal chelates, etc.) as well as molecules that may be indirectly detected by production of a detectable reaction product (e.g., enzymes such as horseradish peroxidase, alkaline phosphatase, etc.) or by a specific binding molecule which itself may be detectable (e.g., biotin, digoxigenin, maltose, oligohistidine, 2,4-dintrobenzene, phenylarsenate, ssDNA, dsDNA, etc.).

Preparation of solid phases and detectable label conjugates often comprise the use of chemical cross-linkers. Cross-linking reagents contain at least two reactive groups, and are divided generally into homofunctional cross-linkers (containing identical reactive groups) and heterofunctional cross-linkers (containing non-identical reactive groups). Homobifunctional cross-linkers that couple through amines, sulfhydryls or react non-specifically are available from many commercial sources. Maleimides, alkyl and aryl halides, alpha-haloacyls and pyridyl disulfides are thiol reactive groups. Maleimides, alkyl and aryl halides, and alpha-haloacyls react with sulfhydryls to form thiol ether bonds, while pyridyl disulfides react with sulfhydryls to produce mixed disulfides. The pyridyl disulfide product is cleavable. Imidoesters are also very useful for protein-protein cross-links. A variety of heterobifunctional cross-linkers, each combining different attributes for successful conjugation, are commercially available.

In certain aspects, the present invention provides kits for the analysis of the described kidney injury markers. The kit comprises reagents for the analysis of at least one test sample which comprise at least one antibody that a kidney injury marker. The kit can also include devices and instructions for performing one or more of the diagnostic and/or prognostic correlations described herein. Preferred kits will comprise an antibody pair for performing a sandwich assay, or a labeled species for performing a competitive assay, for the analyte. Preferably, an antibody pair comprises a first antibody conjugated to a solid phase and a second antibody conjugated to a detectable label, wherein each of the first and second antibodies that bind a kidney injury marker. Most preferably each of the antibodies are monoclonal antibodies. The instructions for use of the kit and performing the correlations can be in the form of labeling, which refers to any written or recorded material that is attached to, or otherwise accompanies a kit at any time during its manufacture, transport, sale or use. For example, the term labeling encompasses advertising leaflets and brochures, packaging materials, instructions, audio or video cassettes, computer discs, as well as writing imprinted directly on kits.

Antibodies

The term “antibody” as used herein refers to a peptide or polypeptide derived from, modeled after or substantially encoded by an immunoglobulin gene or immunoglobulin genes, or fragments thereof, capable of specifically binding an antigen or epitope. See, e.g. Fundamental Immunology, 3rd Edition, W. E. Paul, ed., Raven Press, N.Y. (1993); Wilson (1994; J. Immunol. Methods 175:267-273; Yarmush (1992) J. Biochem. Biophys. Methods 25:85-97. The term antibody includes antigen-binding portions, i.e., “antigen binding sites,” (e.g., fragments, subsequences, complementarity determining regions (CDRs)) that retain capacity to bind antigen, including (i) a Fab fragment, a monovalent fragment consisting of the VL, VH, CL and CHl domains; (ii) a F(ab′)2 fragment, a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) a Fd fragment consisting of the VH and CHl domains; (iv) a Fv fragment consisting of the VL and VH domains of a single arm of an antibody, (v) a dAb fragment (Ward et al., (1989) Nature 341:544-546), which consists of a VH domain; and (vi) an isolated complementarity determining region (CDR). Single chain antibodies are also included by reference in the term “antibody.”

Antibodies used in the immunoassays described herein preferably specifically bind to a kidney injury marker of the present invention. The term “specifically binds” is not intended to indicate that an antibody binds exclusively to its intended target since, as noted above, an antibody binds to any polypeptide displaying the epitope(s) to which the antibody binds. Rather, an antibody “specifically binds” if its affinity for its intended target is about 5-fold greater when compared to its affinity for a non-target molecule which does not display the appropriate epitope(s). Preferably the affinity of the antibody will be at least about 5 fold, preferably 10 fold, more preferably 25-fold, even more preferably 50-fold, and most preferably 100-fold or more, greater for a target molecule than its affinity for a non-target molecule. In preferred embodiments, Preferred antibodies bind with affinities of at least about 10⁷ M⁻¹, and preferably between about 10⁸ M⁻¹ to about 10⁹ M⁻¹, about 10⁹ M⁻¹ to about 10¹⁰ M⁻¹, or about 10¹⁰ M⁻¹ to about 10¹² M⁻¹.

Affinity is calculated as K_(d)=k_(off)/k_(on) (k_(off) is the dissociation rate constant, K_(on) is the association rate constant and K_(d) is the equilibrium constant). Affinity can be determined at equilibrium by measuring the fraction bound (r) of labeled ligand at various concentrations (c). The data are graphed using the Scatchard equation: r/c=K(n−r): where r=moles of bound ligand/mole of receptor at equilibrium; c=free ligand concentration at equilibrium; K=equilibrium association constant; and n=number of ligand binding sites per receptor molecule. By graphical analysis, r/c is plotted on the Y-axis versus r on the X-axis, thus producing a Scatchard plot. Antibody affinity measurement by Scatchard analysis is well known in the art. See, e.g., van Erp et al., J. Immunoassay 12: 425-43, 1991; Nelson and Griswold, Comput. Methods Programs Biomed. 27: 65-8, 1988.

The term “epitope” refers to an antigenic determinant capable of specific binding to an antibody. Epitopes usually consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and usually have specific three dimensional structural characteristics, as well as specific charge characteristics. Conformational and nonconformational epitopes are distinguished in that the binding to the former but not the latter is lost in the presence of denaturing solvents.

Numerous publications discuss the use of phage display technology to produce and screen libraries of polypeptides for binding to a selected analyte. See, e.g, Cwirla et al., Proc. Natl. Acad. Sci. USA 87, 6378-82, 1990; Devlin et al., Science 249, 404-6, 1990, Scott and Smith, Science 249, 386-88, 1990; and Ladner et al., U.S. Pat. No. 5,571,698. A basic concept of phage display methods is the establishment of a physical association between DNA encoding a polypeptide to be screened and the polypeptide. This physical association is provided by the phage particle, which displays a polypeptide as part of a capsid enclosing the phage genome which encodes the polypeptide. The establishment of a physical association between polypeptides and their genetic material allows simultaneous mass screening of very large numbers of phage bearing different polypeptides. Phage displaying a polypeptide with affinity to a target bind to the target and these phage are enriched by affinity screening to the target. The identity of polypeptides displayed from these phage can be determined from their respective genomes. Using these methods a polypeptide identified as having a binding affinity for a desired target can then be synthesized in bulk by conventional means. See, e.g., U.S. Pat. No. 6,057,098, which is hereby incorporated in its entirety, including all tables, figures, and claims.

The antibodies that are generated by these methods may then be selected by first screening for affinity and specificity with the purified polypeptide of interest and, if required, comparing the results to the affinity and specificity of the antibodies with polypeptides that are desired to be excluded from binding. The screening procedure can involve immobilization of the purified polypeptides in separate wells of microtiter plates. The solution containing a potential antibody or groups of antibodies is then placed into the respective microtiter wells and incubated for about 30 min to 2 h. The microtiter wells are then washed and a labeled secondary antibody (for example, an anti-mouse antibody conjugated to alkaline phosphatase if the raised antibodies are mouse antibodies) is added to the wells and incubated for about 30 min and then washed. Substrate is added to the wells and a color reaction will appear where antibody to the immobilized polypeptide(s) are present.

The antibodies so identified may then be further analyzed for affinity and specificity in the assay design selected. In the development of immunoassays for a target protein, the purified target protein acts as a standard with which to judge the sensitivity and specificity of the immunoassay using the antibodies that have been selected. Because the binding affinity of various antibodies may differ; certain antibody pairs (e.g., in sandwich assays) may interfere with one another sterically, etc., assay performance of an antibody may be a more important measure than absolute affinity and specificity of an antibody.

While the present application describes antibody-based binding assays in detail, alternatives to antibodies as binding species in assays are well known in the art. These include receptors for a particular target, aptamers, etc. Aptamers are oligonucleic acid or peptide molecules that bind to a specific target molecule. Aptamers are usually created by selecting them from a large random sequence pool, but natural aptamers also exist. High-affinity aptamers containing modified nucleotides conferring improved characteristics on the ligand, such as improved in vivo stability or improved delivery characteristics. Examples of such modifications include chemical substitutions at the ribose and/or phosphate and/or base positions, and may include amino acid side chain functionalities.

Assay Correlations

The term “correlating” as used herein in reference to the use of biomarkers refers to comparing the presence or amount of the biomarker(s) in a patient to its presence or amount in persons known to suffer from, or known to be at risk of, a given condition; or in persons known to be free of a given condition. Often, this takes the form of comparing an assay result in the form of a biomarker concentration to a predetermined threshold selected to be indicative of the occurrence or nonoccurrence of a disease or the likelihood of some future outcome.

Selecting a diagnostic threshold involves, among other things, consideration of the probability of disease, distribution of true and false diagnoses at different test thresholds, and estimates of the consequences of treatment (or a failure to treat) based on the diagnosis. For example, when considering administering a specific therapy which is highly efficacious and has a low level of risk, few tests are needed because clinicians can accept substantial diagnostic uncertainty. On the other hand, in situations where treatment options are less effective and more risky, clinicians often need a higher degree of diagnostic certainty. Thus, cost/benefit analysis is involved in selecting a diagnostic threshold.

Suitable thresholds may be determined in a variety of ways. For example, one recommended diagnostic threshold for the diagnosis of acute myocardial infarction using cardiac troponin is the 97.5th percentile of the concentration seen in a normal population. Another method may be to look at serial samples from the same patient, where a prior “baseline” result is used to monitor for temporal changes in a biomarker level.

Population studies may also be used to select a decision threshold. Reciever Operating Characteristic (“ROC”) arose from the field of signal detection theory developed during World War II for the analysis of radar images, and ROC analysis is often used to select a threshold able to best distinguish a “diseased” subpopulation from a “nondiseased” subpopulation. A false positive in this case occurs when the person tests positive, but actually does not have the disease. A false negative, on the other hand, occurs when the person tests negative, suggesting they are healthy, when they actually do have the disease. To draw a ROC curve, the true positive rate (TPR) and false positive rate (FPR) are determined as the decision threshold is varied continuously. Since TPR is equivalent with sensitivity and FPR is equal to 1-specificity, the ROC graph is sometimes called the sensitivity vs (1-specificity) plot. A perfect test will have an area under the ROC curve of 1.0; a random test will have an area of 0.5. A threshold is selected to provide an acceptable level of specificity and sensitivity.

In this context, “diseased” is meant to refer to a population having one characteristic (the presence of a disease or condition or the occurrence of some outcome) and “nondiseased” is meant to refer to a population lacking the characteristic. While a single decision threshold is the simplest application of such a method, multiple decision thresholds may be used. For example, below a first threshold, the absence of disease may be assigned with relatively high confidence, and above a second threshold the presence of disease may also be assigned with relatively high confidence. Between the two thresholds may be considered indeterminate. This is meant to be exemplary in nature only.

In addition to threshold comparisons, other methods for correlating assay results to a patient classification (occurrence or nonoccurrence of disease, likelihood of an outcome, etc.) include decision trees, rule sets, Bayesian methods, and neural network methods. These methods can produce probability values representing the degree to which a subject belongs to one classification out of a plurality of classifications.

Measures of test accuracy may be obtained as described in Fischer et al., Intensive Care Med. 29: 1043-51, 2003, and used to determine the effectiveness of a given biomarker. These measures include sensitivity and specificity, predictive values, likelihood ratios, diagnostic odds ratios, and ROC curve areas. The area under the curve (“AUC”) of a ROC plot is equal to the probability that a classifier will rank a randomly chosen positive instance higher than a randomly chosen negative one. The area under the ROC curve may be thought of as equivalent to the Mann-Whitney U test, which tests for the median difference between scores obtained in the two groups considered if the groups are of continuous data, or to the Wilcoxon test of ranks.

As discussed above, suitable tests may exhibit one or more of the following results on these various measures: a specificity of greater than 0.5, preferably at least 0.6, more preferably at least 0.7, still more preferably at least 0.8, even more preferably at least 0.9 and most preferably at least 0.95, with a corresponding sensitivity greater than 0.2, preferably greater than 0.3, more preferably greater than 0.4, still more preferably at least 0.5, even more preferably 0.6, yet more preferably greater than 0.7, still more preferably greater than 0.8, more preferably greater than 0.9, and most preferably greater than 0.95; a sensitivity of greater than 0.5, preferably at least 0.6, more preferably at least 0.7, still more preferably at least 0.8, even more preferably at least 0.9 and most preferably at least 0.95, with a corresponding specificity greater than 0.2, preferably greater than 0.3, more preferably greater than 0.4, still more preferably at least 0.5, even more preferably 0.6, yet more preferably greater than 0.7, still more preferably greater than 0.8, more preferably greater than 0.9, and most preferably greater than 0.95; at least 75% sensitivity, combined with at least 75% specificity; a ROC curve area of greater than 0.5, preferably at least 0.6, more preferably 0.7, still more preferably at least 0.8, even more preferably at least 0.9, and most preferably at least 0.95; an odds ratio different from 1, preferably at least about 2 or more or about 0.5 or less, more preferably at least about 3 or more or about 0.33 or less, still more preferably at least about 4 or more or about 0.25 or less, even more preferably at least about 5 or more or about 0.2 or less, and most preferably at least about 10 or more or about 0.1 or less; a positive likelihood ratio (calculated as sensitivity/(1-specificity)) of greater than 1, at least 2, more preferably at least 3, still more preferably at least 5, and most preferably at least 10; and or a negative likelihood ratio (calculated as (1-sensitivity)/specificity) of less than 1, less than or equal to 0.5, more preferably less than or equal to 0.3, and most preferably less than or equal to 0.1

Additional clinical indicia may be combined with the kidney injury marker assay result(s) of the present invention. These include other biomarkers related to renal status. Examples include the following, which recite the common biomarker name, followed by the Swiss-Prot entry number for that biomarker or its parent: Actin (P68133); Adenosine deaminase binding protein (DPP4, P27487); Alpha-1-acid glycoprotein 1 (P02763); Alpha-1-microglobulin (P02760); Albumin (P02768); Angiotensinogenase (Renin, P00797); Annexin A2 (P07355); Beta-glucuronidase (P08236); B-2-microglobulin (P61679); Beta-galactosidase (P16278); BMP-7 (P18075); Brain natriuretic peptide (proBNP, BNP-32, NTproBNP; P16860); Calcium-binding protein Beta (S100-beta, P04271); Carbonic anhydrase (Q16790); Casein Kinase 2 (P68400); Ceruloplasmin (P00450); Clusterin (P10909); Complement C3 (P01024); Cysteine-rich protein (CYR61, O00622); Cytochrome C(P99999); Epidermal growth factor (EGF, P01133); Endothelin-1 (P05305); Exosomal Fetuin-A (P02765); Fatty acid-binding protein, heart (FABP3, P05413); Fatty acid-binding protein, liver (P07148); Ferritin (light chain, P02793; heavy chain P02794); Fructose-1,6-biphosphatase (P09467); GRO-alpha (CXCL1, (P09341); Growth Hormone (P01241); Hepatocyte growth factor (P14210); Insulin-like growth factor I (P01343); Immunoglobulin G; Immunoglobulin Light Chains (Kappa and Lambda); Interferon gamma (P01308); Lysozyme (P61626); Interleukin-1alpha (P01583); Interleukin-2 (P60568); Interleukin-4 (P60568); Interleukin-9 (P15248); Interleukin-12p40 (P29460); Interleukin-13 (P35225); Interleukin-16 (Q14005); L1 cell adhesion molecule (P32004); Lactate dehydrogenase (P00338); Leucine Aminopeptidase (P28838); Meprin A-alpha subunit (Q16819); Meprin A-beta subunit (Q16820); Midkine (P21741); MIP2-alpha (CXCL2, P19875); MMP-2 (P08253); MMP-9 (P14780); Netrin-1 (O95631); Neutral endopeptidase (P08473); Osteopontin (P10451); Renal papillary antigen 1 (RPA1); Renal papillary antigen 2 (RPA2); Retinol binding protein (P09455); Ribonuclease; S100 calcium-binding protein A6 (P06703); Serum Amyloid P Component (P02743); Sodium/Hydrogen exchanger isoform (NHE3, P48764); Spermidine/spermine N1-acetyltransferase (P21673); TGF-Beta1 (P01137); Transferrin (P02787); Trefoil factor 3 (TFF3, Q07654); Toll-Like protein 4 (O00206); Total protein; Tubulointerstitial nephritis antigen (Q9UJW2); Uromodulin (Tamm-Horsfall protein, P07911).

For purposes of risk stratification, Adiponectin (Q15848); Alkaline phosphatase (P05186); Aminopeptidase N(P15144); CalbindinD28k (P05937); Cystatin C(P01034); 8 subunit of FIFO ATPase (P03928); Gamma-glutamyltransferase (P19440); GSTa (alpha-glutathione-S-transferase, P08263); GSTpi (Glutathione-S-transferase P; GST class-pi; P09211); IGFBP-1 (P08833); IGFBP-2 (P18065); IGFBP-6 (P24592); Integral membrane protein 1 (Itm 1, P46977); Interleukin-6 (P05231); Interleukin-8 (P10145); Interleukin-18 (Q14116); IP-10 (10 kDa interferon-gamma-induced protein, P02778); IRPR (IFRD1, O00458); Isovaleryl-CoA dehydrogenase (IVD, P26440); I-TAC/CXCL11 (O14625); Keratin 19 (P08727); Kim-1 (Hepatitis A virus cellular receptor 1, O43656); L-arginine:glycine amidinotransferase (P50440); Leptin (P41159); Lipocalin2 (NGAL, P80188); MCP-1 (P13500); MIG (Gamma-interferon-induced monokine Q07325); MIP-1a (P10147); MIP-3a (P78556); MIP-1beta (P13236); MIP-1d (Q16663); NAG (N-acetyl-beta-D-glucosaminidase, P54802); Organic ion transporter (OCT2, O15244); Osteoprotegerin (O14788); P8 protein (O60356); Plasminogen activator inhibitor 1 (PAI-1, P05121); ProANP (1-98) (P01160); Protein phosphatase 1-beta (PPI-beta, P62140); Rab GDI-beta (P50395); Renal kallikrein (Q86U61); RT1.B-1 (alpha) chain of the integral membrane protein (Q5Y7A8); Soluble tumor necrosis factor receptor superfamily member 1A (sTNFR-I, P19438); Soluble tumor necrosis factor receptor superfamily member 1B (sTNFR-II, P20333); Tissue inhibitor of metalloproteinases 3 (TIMP-3, P35625); uPAR (Q03405) may be combined with the kidney injury marker assay result(s) of the present invention.

Other clinical indicia which may be combined with the kidney injury marker assay result(s) of the present invention includes demographic information (e.g., weight, sex, age, race), medical history (e.g., family history, type of surgery, pre-existing disease such as aneurism, congestive heart failure, preeclampsia, eclampsia, diabetes mellitus, hypertension, coronary artery disease, proteinuria, renal insufficiency, or sepsis, type of toxin exposure such as NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin), clinical variables (e.g., blood pressure, temperature, respiration rate), risk scores (APACHE score, PREDICT score, TIMI Risk Score for UA/NSTEMI, Framingham Risk Score), a urine total protein measurement, a glomerular filtration rate, an estimated glomerular filtration rate, a urine production rate, a serum or plasma creatinine concentration, a renal papillary antigen 1 (RPA1) measurement; a renal papillary antigen 2 (RPA2) measurement; a urine creatinine concentration, a fractional excretion of sodium, a urine sodium concentration, a urine creatinine to serum or plasma creatinine ratio, a urine specific gravity, a urine osmolality, a urine urea nitrogen to plasma urea nitrogen ratio, a plasma BUN to creatnine ratio, and/or a renal failure index calculated as urine sodium/(urine creatinine/plasma creatinine). Other measures of renal function which may be combined with the kidney injury marker assay result(s) are described hereinafter and in Harrison's Principles of Internal Medicine, 17^(th) Ed., McGraw Hill, New York, pages 1741-1830, and Current Medical Diagnosis & Treatment 2008, 47^(th) Ed, McGraw Hill, New York, pages 785-815, each of which are hereby incorporated by reference in their entirety.

Combining assay results/clinical indicia in this manner can comprise the use of multivariate logistical regression, loglinear modeling, neural network analysis, n-of-m analysis, decision tree analysis, etc. This list is not meant to be limiting.

Diagnosis of Acute Renal Failure

As noted above, the terms “acute renal (or kidney) injury” and “acute renal (or kidney) failure” as used herein are defined in part in terms of changes in serum creatinine from a baseline value. Most definitions of ARF have common elements, including the use of serum creatinine and, often, urine output. Patients may present with renal dysfunction without an available baseline measure of renal function for use in this comparison. In such an event, one may estimate a baseline serum creatinine value by assuming the patient initially had a normal GFR. Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Glomerular filtration rate (GFR) can be calculated by measuring any chemical that has a steady level in the blood, and is freely filtered but neither reabsorbed nor secreted by the kidneys. GFR is typically expressed in units of ml/min:

${G\; F\; R} = \frac{{Urine}\mspace{14mu}{Concentration} \times {Urine}\mspace{14mu}{Flow}}{{Plasma}\mspace{14mu}{Concentration}}$

By normalizing the GFR to the body surface area, a GFR of approximately 75-100 ml/min per 1.73 m² can be assumed. The rate therefore measured is the quantity of the substance in the urine that originated from a calculable volume of blood.

There are several different techniques used to calculate or estimate the glomerular filtration rate (GFR or eGFR). In clinical practice, however, creatinine clearance is used to measure GFR. Creatinine is produced naturally by the body (creatinine is a metabolite of creatine, which is found in muscle). It is freely filtered by the glomerulus, but also actively secreted by the renal tubules in very small amounts such that creatinine clearance overestimates actual GFR by 10-20%. This margin of error is acceptable considering the ease with which creatinine clearance is measured.

Creatinine clearance (CCr) can be calculated if values for creatinine's urine concentration (U_(Cr)), urine flow rate (V), and creatinine's plasma concentration (P_(Cr)) are known. Since the product of urine concentration and urine flow rate yields creatinine's excretion rate, creatinine clearance is also said to be its excretion rate (U_(Cr)×V) divided by its plasma concentration. This is commonly represented mathematically as:

$C_{Cr} = \frac{U_{Cr} \times V}{P_{Cr}}$

Commonly a 24 hour urine collection is undertaken, from empty-bladder one morning to the contents of the bladder the following morning, with a comparative blood test then taken:

$C_{Cr} = \frac{U_{Cr} \times 24\text{-}{hour}\mspace{14mu}{volume}}{P_{Cr} \times 24 \times 60\mspace{14mu}{mins}}$

To allow comparison of results between people of different sizes, the CCr is often corrected for the body surface area (BSA) and expressed compared to the average sized man as ml/min/1.73 m2. While most adults have a BSA that approaches 1.7 (1.6-1.9), extremely obese or slim patients should have their CCr corrected for their actual BSA:

$C_{{Cr} - {corrected}} = \frac{C_{Cr} \times 1.73}{B\; S\; A}$

The accuracy of a creatinine clearance measurement (even when collection is complete) is limited because as glomerular filtration rate (GFR) falls creatinine secretion is increased, and thus the rise in serum creatinine is less. Thus, creatinine excretion is much greater than the filtered load, resulting in a potentially large overestimation of the GFR (as much as a twofold difference). However, for clinical purposes it is important to determine whether renal function is stable or getting worse or better. This is often determined by monitoring serum creatinine alone. Like creatinine clearance, the serum creatinine will not be an accurate reflection of GFR in the non-steady-state condition of ARF. Nonetheless, the degree to which serum creatinine changes from baseline will reflect the change in GFR. Serum creatinine is readily and easily measured and it is specific for renal function.

For purposes of determining urine output on a Urine output on a mL/kg/hr basis, hourly urine collection and measurement is adequate. In the case where, for example, only a cumulative 24-h output was available and no patient weights are provided, minor modifications of the RIFLE urine output criteria have been described. For example, Bagshaw et al., Nephrol. Dial. Transplant. 23: 1203-1210, 2008, assumes an average patient weight of 70 kg, and patients are assigned a RIFLE classification based on the following: <35 mL/h (Risk), <21 mL/h (Injury) or <4 mL/h (Failure).

Selecting a Treatment Regimen

Once a diagnosis is obtained, the clinician can readily select a treatment regimen that is compatible with the diagnosis, such as initiating renal replacement therapy, withdrawing delivery of compounds that are known to be damaging to the kidney, kidney transplantation, delaying or avoiding procedures that are known to be damaging to the kidney, modifying diuretic administration, initiating goal directed therapy, etc. The skilled artisan is aware of appropriate treatments for numerous diseases discussed in relation to the methods of diagnosis described herein. See, e.g., Merck Manual of Diagnosis and Therapy, 17th Ed. Merck Research Laboratories, Whitehouse Station, N.J., 1999. In addition, since the methods and compositions described herein provide prognostic information, the markers of the present invention may be used to monitor a course of treatment. For example, improved or worsened prognostic state may indicate that a particular treatment is or is not efficacious.

One skilled in the art readily appreciates that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The examples provided herein are representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention.

EXAMPLE 1 Contrast-induced Nephropathy Sample Collection

The objective of this sample collection study is to collect samples of plasma and urine and clinical data from patients before and after receiving intravascular contrast media. Approximately 250 adults undergoing radiographic/angiographic procedures involving intravascular administration of iodinated contrast media are enrolled. To be enrolled in the study, each patient must meet all of the following inclusion criteria and none of the following exclusion criteria:

Inclusion Criteria

-   males and females 18 years of age or older; -   undergoing a radiographic/angiographic procedure (such as a CT scan     or coronary intervention) involving the intravascular administration     of contrast media; -   expected to be hospitalized for at least 48 hours after contrast     administration. -   able and willing to provide written informed consent for study     participation and to comply with all study procedures.     Exclusion Criteria -   renal transplant recipients; -   acutely worsening renal function prior to the contrast procedure; -   already receiving dialysis (either acute or chronic) or in imminent     need of dialysis at enrollment; -   expected to undergo a major surgical procedure (such as involving     cardiopulmonary bypass) or an additional imaging procedure with     contrast media with significant risk for further renal insult within     the 48 hrs following contrast administration; -   participation in an interventional clinical study with an     experimental therapy within the previous 30 days; -   known infection with human immunodeficiency virus (HIV) or a     hepatitis virus.

Immediately prior to the first contrast administration (and after any pre-procedure hydration), an EDTA anti-coagulated blood sample (10 mL) and a urine sample (10 mL) are collected from each patient. Blood and urine samples are then collected at 4 (±0.5), 8 (±1), 24 (±2) 48 (±2), and 72 (±2) hrs following the last administration of contrast media during the index contrast procedure. Blood is collected via direct venipuncture or via other available venous access, such as an existing femoral sheath, central venous line, peripheral intravenous line or hep-lock. These study blood samples are processed to plasma at the clinical site, frozen and shipped to Astute Medical, Inc., San Diego, Calif. The study urine samples are frozen and shipped to Astute Medical, Inc.

Serum creatinine is assessed at the site immediately prior to the first contrast administration (after any pre-procedure hydration) and at 4 (±0.5), 8 (±1), 24 (±2) and 48 (±2)), and 72 (±2) hours following the last administration of contrast (ideally at the same time as the study samples are obtained). In addition, each patient's status is evaluated through day 30 with regard to additional serum and urine creatinine measurements, a need for dialysis, hospitalization status, and adverse clinical outcomes (including mortality).

Prior to contrast administration, each patient is assigned a risk based on the following assessment: systolic blood pressure<80 mm Hg=5 points; intra-arterial balloon pump=5 points; congestive heart failure (Class III-IV or history of pulmonary edema)=5 points; age>75 yrs=4 points; hematocrit level<39% for men, <35% for women=3 points; diabetes=3 points; contrast media volume=1 point for each 100 mL; serum creatinine level>1.5 g/dL=4 points OR estimated GFR 40-60 mL/min/1.73 m²=2 points, 20-40 mL/min/1.73 m²=4 points, <20 mL/min/1.73 m²=6 points. The risks assigned are as follows: risk for CIN and dialysis: 5 or less total points=risk of CIN—7.5%, risk of dialysis—0.04%; 6-10 total points=risk of CIN—14%, risk of dialysis—0.12%; 11-16 total points=risk of CIN—26.1%, risk of dialysis—1.09%; >16 total points=risk of CIN—57.3%, risk of dialysis—12.8%.

EXAMPLE 2 Cardiac Surgery Sample Collection

The objective of this sample collection study is to collect samples of plasma and urine and clinical data from patients before and after undergoing cardiovascular surgery, a procedure known to be potentially damaging to kidney function. Approximately 900 adults undergoing such surgery are enrolled. To be enrolled in the study, each patient must meet all of the following inclusion criteria and none of the following exclusion criteria:

Inclusion Criteria

-   males and females 18 years of age or older; -   undergoing cardiovascular surgery; -   Toronto/Ottawa Predictive Risk Index for Renal Replacement risk     score of at least 2 (Wijeysundera et al., JAMA 297: 1801-9, 2007);     and -   able and willing to provide written informed consent for study     participation and to comply with all study procedures.     Exclusion Criteria -   known pregnancy; -   previous renal transplantation; -   acutely worsening renal function prior to enrollment (e.g., any     category of RIFLE criteria); -   already receiving dialysis (either acute or chronic) or in imminent     need of dialysis at enrollment; -   currently enrolled in another clinical study or expected to be     enrolled in another clinical study within 7 days of cardiac surgery     that involves drug infusion or a therapeutic intervention for AKI; -   known infection with human immunodeficiency virus (HIV) or a     hepatitis virus.

Within 3 hours prior to the first incision (and after any pre-procedure hydration), an EDTA anti-coagulated blood sample (10 mL), whole blood (3 mL), and a urine sample (35 mL) are collected from each patient. Blood and urine samples are then collected at 3 (±0.5), 6 (±0.5), 12 (±1), 24 (±2) and 48 (±2) hrs following the procedure and then daily on days 3 through 7 if the subject remains in the hospital. Blood is collected via direct venipuncture or via other available venous access, such as an existing femoral sheath, central venous line, peripheral intravenous line or hep-lock. These study blood samples are frozen and shipped to Astute Medical, Inc., San Diego, Calif. The study urine samples are frozen and shipped to Astute Medical, Inc.

EXAMPLE 3 Acutely Ill Subject Sample Collection

The objective of this study is to collect samples from acutely ill patients. Approximately 900 adults expected to be in the ICU for at least 48 hours will be enrolled. To be enrolled in the study, each patient must meet all of the following inclusion criteria and none of the following exclusion criteria:

Inclusion Criteria

-   males and females 18 years of age or older; -   Study population 1: approximately 300 patients that have at least     one of: -   shock (SBP<90 mmHg and/or need for vasopressor support to maintain     MAP>60 mmHg and/or documented drop in SBP of at least 40 mmHg); and     sepsis; -   Study population 2: approximately 300 patients that have at least     one of: -   IV antibiotics ordered in computerized physician order entry (CPOE)     within 24 hours of enrollment; -   contrast media exposure within 24 hours of enrollment; -   increased Intra-Abdominal Pressure with acute decompensated heart     failure; and -   severe trauma as the primary reason for ICU admission and likely to     be hospitalized in the ICU for 48 hours after enrollment; -   Study population 3: approximately 300 patients expected to be     hospitalized through acute care setting (ICU or ED) with a known     risk factor for acute renal injury (e.g. sepsis, hypotension/shock     (Shock=systolic BP<90 mmHg and/or the need for vasopressor support     to maintain a MAP>60 mmHg and/or a documented drop in SBP>40 mmHg),     major trauma, hemorrhage, or major surgery); and/or expected to be     hospitalized to the ICU for at least 24 hours after enrollment.     Exclusion Criteria -   known pregnancy; -   institutionalized individuals; -   previous renal transplantation; -   known acutely worsening renal function prior to enrollment (e.g.,     any category of RIFLE criteria); -   received dialysis (either acute or chronic) within 5 days prior to     enrollment or in imminent need of dialysis at the time of     enrollment; -   known infection with human immunodeficiency virus (HIV) or a     hepatitis virus; -   meets only the SBP<90 mmHg inclusion criterion set forth above, and     does not have shock in the attending physician's or principal     investigator's opinion.

After providing informed consent, an EDTA anti-coagulated blood sample (10 mL) and a urine sample (25-30 mL) are collected from each patient. Blood and urine samples are then collected at 4 (±0.5) and 8 (±1) hours after contrast administration (if applicable); at 12 (±1), 24 (±2), and 48 (±2) hours after enrollment, and thereafter daily up to day 7 to day 14 while the subject is hospitalized. Blood is collected via direct venipuncture or via other available venous access, such as an existing femoral sheath, central venous line, peripheral intravenous line or hep-lock. These study blood samples are processed to plasma at the clinical site, frozen and shipped to Astute Medical, Inc., San Diego, Calif. The study urine samples are frozen and shipped to Astute Medical, Inc.

EXAMPLE 4 Immunoassay Format

Analytes are measured using standard sandwich enzyme immunoassay techniques. A first antibody which binds the analyte is immobilized in wells of a 96 well polystyrene microplate. Analyte standards and test samples are pipetted into the appropriate wells and any analyte present is bound by the immobilized antibody. After washing away any unbound substances, a horseradish peroxidase-conjugated second antibody which binds the analyte is added to the wells, thereby forming sandwich complexes with the analyte (if present) and the first antibody. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution comprising tetramethylbenzidine and hydrogen peroxide is added to the wells. Color develops in proportion to the amount of analyte present in the sample. The color development is stopped and the intensity of the color is measured at 540 nm or 570 nm. An analyte concentration is assigned to the test sample by comparison to a standard curve determined from the analyte standards. Concentrations reported below are as follows: Cathepsin B ng/mL; Renin pg/mL; Dipeptidyl Peptidase IV (soluble form) ng/mL; Neprilysin (soluble form) ng/mL; Beta-2-microglobulin μg/mL; Carbonic anhydrase IX (soluble form) ng/mL; and C-X-C motif chemokine 2 pg/mL.

EXAMPLE 5 Apparently Healthy Donor and Chronic Disease Patient Samples

Human urine samples from donors with no known chronic or acute disease (“Apparently Healthy Donors”) were purchased from two vendors (Golden West Biologicals, Inc., 27625 Commerce Center Dr., Temecula, Calif. 92590 and Virginia Medical Research, Inc., 915 First Colonial Rd., Virginia Beach, Va. 23454). The urine samples were shipped and stored frozen at less than −20° C. The vendors supplied demographic information for the individual donors including gender, race (Black/White), smoking status and age.

Human urine samples from donors with various chronic diseases (“Chronic Disease Patients”) including congestive heart failure, coronary artery disease, chronic kidney disease, chronic obstructive pulmonary disease, diabetes mellitus and hypertension were purchased from Virginia Medical Research, Inc., 915 First Colonial Rd., Virginia Beach, Va. 23454. The urine samples were shipped and stored frozen at less than −20 degrees centigrade. The vendor provided a case report form for each individual donor with age, gender, race (Black/White), smoking status and alcohol use, height, weight, chronic disease(s) diagnosis, current medications and previous surgeries.

EXAMPLE 6 Use of Kidney Injury Markers for Evaluating Renal Status in Patients

Patients from the intensive care unit (ICU) were enrolled in the following study. Each patient was classified by kidney status as non-injury (0), risk of injury (R), injury (I), and failure (F) according to the maximum stage reached within 7 days of enrollment as determined by the RIFLE criteria. EDTA anti-coagulated blood samples (10 mL) and a urine samples (25-30 mL) were collected from each patient at enrollment, 4 (±0.5) and 8 (±1) hours after contrast administration (if applicable); at 12 (±1), 24 (±2), and 48 (±2) hours after enrollment, and thereafter daily up to day 7 to day 14 while the subject is hospitalized. Markers were each measured by standard immunoassay methods using commercially available assay reagents in the urine samples and the plasma component of the blood samples collected.

Two cohorts were defined to represent a “diseased” and a “normal” population. While these terms are used for convenience, “diseased” and “normal” simply represent two cohorts for comparison (say RIFLE 0 vs RIFLE R, I and F; RIFLE 0 vs RIFLE R; RIFLE 0 and R vs RIFLE I and F; etc.). The time “prior max stage” represents the time at which a sample is collected, relative to the time a particular patient reaches the lowest disease stage as defined for that cohort, binned into three groups which are +/−12 hours. For example, “24 hr prior” which uses 0 vs R, I, F as the two cohorts would mean 24 hr (+/−12 hours) prior to reaching stage R (or I if no sample at R, or F if no sample at R or I).

A receiver operating characteristic (ROC) curve was generated for each biomarker measured and the area under each ROC curve (AUC) is determined. Patients in Cohort 2 were also separated according to the reason for adjudication to cohort 2 as being based on serum creatinine measurements (sCr), being based on urine output (UO), or being based on either serum creatinine measurements or urine output. Using the same example discussed above (0 vs R, I, F), for those patients adjudicated to stage R, I, or F on the basis of serum creatinine measurements alone, the stage 0 cohort may include patients adjudicated to stage R, I, or F on the basis of urine output; for those patients adjudicated to stage R, I, or F on the basis of urine output alone, the stage 0 cohort may include patients adjudicated to stage R, I, or F on the basis of serum creatinine measurements; and for those patients adjudicated to stage R, I, or F on the basis of serum creatinine measurements or urine output, the stage 0 cohort contains only patients in stage 0 for both serum creatinine measurements and urine output. Also, in the data for patients adjudicated on the basis of serum creatinine measurements or urine output, the adjudication method which yielded the most severe RIFLE stage is used.

The ability to distinguish cohort 1 from Cohort 2 was determined using ROC analysis. SE is the standard error of the AUC, n is the number of sample or individual patients (“pts,” as indicated). Standard errors are calculated as described in Hanley, J. A., and McNeil, B. J., The meaning and use of the area under a receiver operating characteristic (ROC) curve. Radiology (1982) 143: 29-36; p values are calculated with a two-tailed Z-test. An AUC<0.5 is indicative of a negative going marker for the comparison, and an AUC>0.5 is indicative of a positive going marker for the comparison.

Various threshold (or “cutoff”) concentrations were selected, and the associated sensitivity and specificity for distinguishing cohort 1 from cohort 2 are determined. OR is the odds ratio calculated for the particular cutoff concentration, and 95% CI is the confidence interval for the odds ratio.

TABLE 1 Comparison of marker levels in urine samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0) and in urine samples collected from subjects at 0, 24 hours, and 48 hours prior to reaching stage R, I or F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 1.44 4.76 1.44 2.61 1.44 4.70 Average 2.57 3.52 2.57 2.83 2.57 3.36 Stdev 2.43 2.58 2.43 2.53 2.43 2.39 p(t-test) 0.014 0.48 0.11 Min 0.00152 0.00403 0.00152 0.00212 0.00152 0.0378 Max 6.10 6.10 6.10 6.07 6.10 5.80 n (Samp) 255 48 255 57 255 27 n (Patient) 103 48 103 57 103 27 sCr only Median 1.43 0.462 1.43 0.763 1.43 1.24 Average 2.59 2.48 2.59 2.51 2.59 2.07 Stdev 2.45 2.78 2.45 2.68 2.45 2.33 p(t-test) 0.86 0.89 0.45 Min 0.00152 0.00925 0.00152 0.0114 0.00152 0.0324 Max 6.10 6.10 6.10 5.80 6.10 5.80 n (Samp) 447 16 447 21 447 13 n (Patient) 170 16 170 21 170 13 UO only Median 1.39 4.57 1.39 2.61 1.39 4.82 Average 2.56 3.58 2.56 2.90 2.56 3.51 Stdev 2.44 2.45 2.44 2.50 2.44 2.41 p(t-test) 0.010 0.37 0.064 Min 0.00152 0.00403 0.00152 0.00212 0.00152 0.0378 Max 6.10 6.10 6.10 6.07 6.10 5.80 n (Samp) 218 46 218 51 218 25 n (Patient) 87 46 87 51 87 25 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.59 0.45 0.60 0.51 0.46 0.51 0.57 0.45 0.58 SE 0.046 0.075 0.048 0.043 0.066 0.045 0.060 0.083 0.063 p 0.044 0.53 0.031 0.83 0.59 0.79 0.25 0.55 0.19 nCohort 1 255 447 218 255 447 218 255 447 218 nCohort 2 48 16 46 57 21 51 27 13 25 Cutoff 1 0.734 0.0999 1.48 0.278 0.153 0.278 1.22 0.171 1.02 Sens 1 71% 75% 72% 70% 71% 71% 70% 77% 72% Spec 1 40% 17% 51% 27% 21% 27% 48% 23% 46% Cutoff 2 0.0999 0.0513 0.278 0.0999 0.0851 0.152 0.213 0.0743 0.354 Sens 2 81% 81% 80% 81% 81% 80% 81% 85% 80% Spec 2 14% 11% 27% 14% 15% 19% 24% 14% 31% Cutoff 3 0.0273 0.0197 0.0298 0.0246 0.0372 0.0168 0.0683 0.0683 0.141 Sens 3 92% 94% 91% 91% 90% 90% 93% 92% 92% Spec 3  4%  4%  5%  3%  8%  2% 10% 13% 18% Cutoff 4 5.08 5.13 5.16 5.08 5.13 5.16 5.08 5.13 5.16 Sens 4 48% 38% 43% 37% 38% 37% 41% 23% 36% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 5.80 5.80 5.80 5.80 5.80 5.80 5.80 5.80 5.80 Sens 5 17%  6% 17%  2%  0%  2%  0%  0%  0% Spec 5 95% 95% 94% 95% 95% 94% 95% 95% 94% Cutoff 6 5.80 5.80 5.80 5.80 5.80 5.80 5.80 5.80 5.80 Sens 6 17%  6% 17%  2%  0%  2%  0%  0%  0% Spec 6 95% 95% 94% 95% 95% 94% 95% 95% 94% OR Quart 2 0.41 0.39 0.52 0.57 0.49 0.51 0.47 1.0 0.57 p Value 0.12 0.27 0.26 0.20 0.32 0.17 0.30 1.0 0.45 95% CI of 0.14 0.074 0.16 0.24 0.12 0.20 0.11 0.20 0.13 OR Quart2 1.2 2.0 1.6 1.3 2.0 1.3 2.0 5.1 2.5 OR Quart 3 1.1 0.59 2.2 0.85 0.83 1.4 1.8 1.0 1.9 p Value 0.85 0.48 0.084 0.68 0.76 0.42 0.29 1.0 0.28 95% CI of 0.45 0.14 0.90 0.38 0.24 0.63 0.61 0.20 0.60 OR Quart3 2.7 2.5 5.4 1.9 2.8 3.1 5.2 5.1 6.1 OR Quart 4 2.1 1.2 1.9 1.1 1.2 0.73 1.4 1.3 1.7 p Value 0.080 0.75 0.18 0.84 0.78 0.48 0.59 0.70 0.40 95% CI of 0.92 0.36 0.75 0.50 0.38 0.30 0.44 0.29 0.51 OR Quart4 4.7 4.1 4.6 2.3 3.6 1.8 4.1 6.2 5.4 C-X-C motif chemokine 2 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.135 2.51 0.135 4.01 0.135 0.0260 Average 8.01 11.4 8.01 12.4 8.01 7.85 Stdev 26.5 27.8 26.5 30.9 26.5 19.6 p(t-test) 0.32 0.17 0.97 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 111 n (Samp) 360 75 360 91 360 43 n (Patient) 190 75 190 91 190 43 sCr only Median 0.536 2.64 0.536 4.37 0.536 3.34 Average 8.92 17.6 8.92 17.4 8.92 6.53 Stdev 25.5 42.4 25.5 40.9 25.5 8.89 p(t-test) 0.083 0.058 0.65 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 36.2 n (Samp) 755 29 755 37 755 23 n (Patient) 295 29 295 37 295 23 UO only Median 0.262 2.64 0.262 5.28 0.262 0.0260 Average 7.67 12.4 7.67 14.9 7.67 9.52 Stdev 25.1 29.6 25.1 33.2 25.1 21.4 p(t-test) 0.18 0.035 0.67 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 111 n (Samp) 315 65 315 78 315 36 n (Patient) 134 65 134 78 134 36 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.61 0.61 0.62 0.62 0.61 0.64 0.49 0.57 0.49 SE 0.037 0.057 0.040 0.034 0.050 0.037 0.047 0.063 0.051 p 0.0039 0.049 0.0025   5.8E−4 0.025 9.7E−5 0.82 0.27 0.83 nCohort 1 360 755 315 360 755 315 360 755 315 nCohort 2 75 29 65 91 37 78 43 23 36 Cutoff 1 0.00804 0.244 0.299 0.00804 0.00804 0.299 0.00804 0.00804 0.00804 Sens 1 100%  72% 71% 100%  100%  71% 100%  100%  100%  Spec 1  0% 46% 51%  0%  0% 51%  0%  0%  0% Cutoff 2 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 Sens 2 100%  100%  100%  100%  100%  100%  100%  100%  100%  Spec 2  0%  0%  0%  0%  0%  0%  0%  0%  0% Cutoff 3 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 Sens 3 100%  100%  100%  100%  100%  100%  100%  100%  100%  Spec 3  0%  0%  0%  0%  0%  0%  0%  0%  0% Cutoff 4 3.08 3.96 3.82 3.08 3.96 3.82 3.08 3.96 3.82 Sens 4 45% 38% 45% 52% 54% 55% 37% 43% 28% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 6.49 7.98 7.00 6.49 7.98 7.00 6.49 7.98 7.00 Sens 5 36% 31% 38% 37% 35% 40% 23% 30% 25% Spec 5 80% 80% 80% 80% 80% 80% 80% 80% 80% Cutoff 6 15.4 20.2 14.9 15.4 20.2 14.9 15.4 20.2 14.9 Sens 6 23% 21% 25% 19% 22% 24% 19%  4% 25% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 0.14 >9.4 0.25 >44 >13 3.1 0.89 >9.4 0.76 p Value 4.8E−4 <0.034 0.010 <2.2E−4 <0.015 0.015 0.81 <0.034 0.60 95% CI of 0.047 >1.2 0.090 >5.9 >1.6 1.2 0.35 >1.2 0.27 OR Quart2 0.42 na 0.72 na na 7.8 2.3 na 2.1 OR Quart 3 0.78 >12 1.1 >30 >11 3.3 0.78 >5.1 0.10 p Value 0.47 <0.019 0.85 <9.4E−4 <0.025 0.0097 0.62 <0.14 0.031 95% CI of 0.40 >1.5 0.51 >4.0 >1.3 1.3 0.30 >0.59 0.012 OR Quart3 1.5 na 2.2 na na 8.3 2.1 na 0.81 OR Quart 4 1.3 >9.4 1.6 >50 >16 6.2 1.7 >9.4 2.5 p Value 0.36 <0.034 0.16 <1.3E−4 <0.0073 4.4E−5 0.20 <0.034 0.040 95% CI of 0.72 >1.2 0.82 >6.7 >2.1 2.6 0.75 >1.2 1.0 OR Quart4 2.5 na 3.3 na na 15 4.0 na 5.8 Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 319 494 319 483 319 323 Average 750 886 750 1350 750 1120 Stdev 1270 1110 1270 3110 1270 1660 p(t-test) 0.53 0.073 0.20 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 9810 5150 9810 21100 9810 5550 n (Samp) 121 45 121 50 121 26 n (Patient) 98 45 98 50 98 26 sCr only Median 394 254 394 565 394 304 Average 978 1150 978 1340 978 985 Stdev 1840 1760 1840 1670 1840 1460 p(t-test) 0.75 0.40 0.99 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 21100 4570 21100 5380 21100 4250 n (Samp) 259 12 259 19 259 13 n (Patient) 159 12 159 19 159 13 UO only Median 297 638 297 606 297 385 Average 758 996 758 1540 758 1290 Stdev 1340 1100 1340 3230 1340 1710 p(t-test) 0.31 0.035 0.10 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 9810 5150 9810 21100 9810 5550 n (Samp) 106 42 106 46 106 23 n (Patient) 82 42 82 46 82 23 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.58 0.46 0.64 0.57 0.56 0.63 0.53 0.47 0.59 SE 0.051 0.087 0.052 0.049 0.070 0.051 0.063 0.083 0.068 p 0.12 0.65 0.0072 0.13 0.42 0.012 0.59 0.76 0.21 nCohort 1 121 259 106 121 259 106 121 259 106 nCohort 2 45 12 42 50 19 46 26 13 23 Cutoff 1 234 161 279 203 84.2 211 123 137 123 Sens 1 71% 75% 71% 70% 74% 72% 73% 77% 74% Spec 1 40% 29% 46% 38% 20% 41% 31% 28% 32% Cutoff 2 177 34.5 224 111 34.5 134 10.6 0 10.6 Sens 2 80% 83% 81% 80% 84% 80% 81% 100%  83% Spec 2 36% 15% 41% 30% 15% 33% 21%  0% 20% Cutoff 3 10.1 0 131 65.6 0 88.6 0 0 7.32 Sens 3 91% 100%  90% 90% 100%  91% 100%  100%  91% Spec 3 21%  0% 33% 27%  0% 28%  0%  0% 18% Cutoff 4 606 881 600 606 881 600 606 881 600 Sens 4 44% 25% 52% 42% 42% 50% 31% 31% 39% Spec 4 70% 70% 71% 70% 70% 71% 70% 70% 71% Cutoff 5 1130 1590 1130 1130 1590 1130 1130 1590 1130 Sens 5 22% 25% 29% 30% 37% 35% 31% 23% 39% Spec 5 80% 80% 80% 80% 80% 80% 80% 80% 80% Cutoff 6 1990 2390 2060 1990 2390 2060 1990 2390 2060 Sens 6 13% 25% 14% 16% 16% 22% 23% 15% 22% Spec 6 90% 90% 91% 90% 90% 91% 90% 90% 91% OR Quart 2 2.9 0.66 6.1 2.1 0.15 2.5 0.97 0.66 0.56 p Value 0.052 0.65 0.0089 0.16 0.085 0.11 0.96 0.65 0.45 95% CI of 0.99 0.11 1.6 0.75 0.018 0.81 0.28 0.11 0.12 OR Quart2 8.6 4.1 24 5.6 1.3 7.5 3.3 4.1 2.6 OR Quart 3 2.1 1.4 5.4 1.6 0.65 2.5 0.97 1.7 1.2 p Value 0.18 0.70 0.015 0.34 0.51 0.11 0.96 0.47 0.74 95% CI of 0.71 0.29 1.4 0.59 0.17 0.81 0.28 0.39 0.34 OR Quart3 6.5 6.3 21 4.6 2.4 7.5 3.3 7.5 4.6 OR Quart 4 2.9 1.0 6.9 2.5 1.4 3.9 1.4 1.0 2.0 p Value 0.052 0.99 0.0052 0.067 0.59 0.014 0.59 1.0 0.26 95% CI of 0.99 0.20 1.8 0.94 0.44 1.3 0.43 0.19 0.60 OR Quart4 8.6 5.2 27 6.8 4.1 11 4.5 5.1 6.9 Cathepsin B 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.504 0.628 0.504 1.15 0.504 0.649 Average 2.26 1.84 2.26 5.00 2.26 4.06 Stdev 8.48 2.68 8.48 11.8 8.48 15.2 p(t-test) 0.74 0.084 0.40 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 72.4 11.0 72.4 64.9 72.4 78.1 n (Samp) 131 47 131 50 131 26 n (Patient) 102 47 102 50 102 26 sCr only Median 0.657 0.485 0.657 1.92 0.657 0.338 Average 2.89 1.92 2.89 4.95 2.89 1.27 Stdev 9.57 2.68 9.57 7.48 9.57 1.85 p(t-test) 0.71 0.36 0.55 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 0.0682 Max 78.1 7.84 78.1 29.7 78.1 6.19 n (Samp) 269 14 269 19 269 13 n (Patient) 162 14 162 19 162 13 UO only Median 0.539 0.951 0.539 1.32 0.539 0.846 Average 2.37 2.21 2.37 5.79 2.37 5.24 Stdev 8.90 2.91 8.90 12.6 8.90 16.1 p(t-test) 0.91 0.052 0.23 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 72.4 11.6 72.4 64.9 72.4 78.1 n (Samp) 118 44 118 46 118 23 n (Patient) 87 44 87 46 87 23 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.56 0.48 0.62 0.63 0.67 0.65 0.50 0.46 0.56 SE 0.050 0.080 0.051 0.048 0.070 0.050 0.062 0.084 0.067 p 0.25 0.83 0.021 0.0072 0.015 0.0032 0.98 0.64 0.41 nCohort 1 131 269 118 131 269 118 131 269 118 nCohort 2 47 14 44 50 19 46 26 13 23 Cutoff 1 0.339 0.142 0.546 0.665 0.797 0.665 0.185 0.265 0.185 Sens 1 70% 71% 70% 70% 74% 72% 73% 77% 74% Spec 1 40% 18% 51% 58% 55% 56% 21% 28% 21% Cutoff 2 0.140 0.0513 0.309 0.245 0.265 0.268 0.105 0.128 0.0764 Sens 2 81% 86% 82% 80% 84% 80% 81% 85% 83% Spec 2 18% 14% 37% 30% 28% 31% 17% 17% 12% Cutoff 3 0 0 0.0764 0 0 0 0 0.0901 0 Sens 3 100%  100%  91% 100%  100%  100%  100%  92% 100%  Spec 3  0%  0% 12%  0%  0%  0%  0% 15%  0% Cutoff 4 1.16 1.35 1.17 1.16 1.35 1.17 1.16 1.35 1.17 Sens 4 36% 36% 45% 50% 63% 54% 27% 23% 39% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 1.81 2.07 2.02 1.81 2.07 2.02 1.81 2.07 2.02 Sens 5 28% 36% 30% 38% 42% 41% 19% 23% 30% Spec 5 80% 80% 81% 80% 80% 81% 80% 80% 81% Cutoff 6 3.53 4.65 3.53 3.53 4.65 3.53 3.53 4.65 3.53 Sens 6 19% 14% 20% 26% 26% 28% 15%  8% 30% Spec 6 90% 90% 91% 90% 90% 91% 90% 90% 91% OR Quart 2 0.85 0.19 2.9 0.44 1.5 0.49 1.7 1.0 0.24 p Value 0.75 0.13 0.071 0.16 0.65 0.25 0.36 0.99 0.092 95% CI of 0.31 0.021 0.91 0.14 0.25 0.15 0.54 0.20 0.047 OR Quart2 2.3 1.7 9.2 1.4 9.4 1.6 5.3 5.2 1.3 OR Quart 3 1.4 0.38 3.0 1.9 1.5 1.8 0.47 1.4 1.0 p Value 0.47 0.26 0.062 0.17 0.65 0.22 0.31 0.70 1.0 95% CI of 0.55 0.072 0.94 0.76 0.25 0.69 0.11 0.29 0.31 OR Quart3 3.7 2.0 9.5 4.9 9.4 4.9 2.0 6.3 3.2 OR Quart 4 1.7 1.2 4.0 2.5 6.3 2.8 1.5 1.0 0.97 p Value 0.27 0.74 0.016 0.054 0.019 0.037 0.52 0.99 0.95 95% CI of 0.66 0.36 1.3 0.99 1.3 1.1 0.46 0.20 0.30 OR Quart4 4.3 4.3 13 6.2 30 7.3 4.7 5.2 3.1 Neprilysin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 1.26 0.949 1.26 1.03 nd nd Average 4.09 2.29 4.09 5.48 nd nd Stdev 8.95 3.70 8.95 13.1 nd nd p(t-test) 0.40 0.60 nd nd Min 0.0532 0.0313 0.0532 0.0902 nd nd Max 51.0 16.0 51.0 46.3 nd nd n (Samp) 62 19 62 19 nd nd n (Patient) 50 19 50 19 nd nd UO only Median 0.963 0.949 0.963 0.896 nd nd Average 2.98 2.47 2.98 5.23 nd nd Stdev 6.67 4.11 6.67 12.8 nd nd p(t-test) 0.78 0.33 nd nd Min 0.0532 0.0313 0.0532 0.0203 nd nd Max 35.3 16.0 35.3 46.3 nd nd n (Samp) 52 15 52 20 nd nd n (Patient) 41 15 41 20 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.43 nd 0.47 0.47 nd 0.50 nd nd nd SE 0.077 nd 0.086 0.077 nd 0.077 nd nd nd p 0.38 nd 0.69 0.74 nd 0.99 nd nd nd nCohort 1 62 nd 52 62 nd 52 nd nd nd nCohort 2 19 nd 15 19 nd 20 nd nd nd Cutoff 1 0.279 nd 0.376 0.586 nd 0.690 nd nd nd Sens 1 74% nd 73% 74% nd 70% nd nd nd Spec 1  8% nd 15% 23% nd 31% nd nd nd Cutoff 2 0.238 nd 0.251 0.351 nd 0.461 nd nd nd Sens 2 84% nd 80% 84% nd 80% nd nd nd Spec 2  8% nd  8% 15% nd 21% nd nd nd Cutoff 3 0.117 nd 0.0869 0.178 nd 0.306 nd nd nd Sens 3 95% nd 93% 95% nd 90% nd nd nd Spec 3  5% nd  4%  6% nd 10% nd nd nd Cutoff 4 1.99 nd 1.45 1.99 nd 1.45 nd nd nd Sens 4 37% nd 33% 21% nd 35% nd nd nd Spec 4 71% nd 71% 71% nd 71% nd nd nd Cutoff 5 3.50 nd 2.26 3.50 nd 2.26 nd nd nd Sens 5 21% nd 33% 16% nd 15% nd nd nd Spec 5 81% nd 81% 81% nd 81% nd nd nd Cutoff 6 10.1 nd 4.43 10.1 nd 4.43 nd nd nd Sens 6  5% nd 13% 11% nd 10% nd nd nd Spec 6 90% nd 90% 90% nd 90% nd nd nd OR Quart 2 0.44 nd 0.51 1.4 nd 1.8 nd nd nd p Value 0.30 nd 0.42 0.65 nd 0.46 nd nd nd 95% CI of 0.094 nd 0.10 0.32 nd 0.40 nd nd nd OR Quart2 2.1 nd 2.6 6.3 nd 7.7 nd nd nd OR Quart 3 0.44 nd 0.32 1.1 nd 1.3 nd nd nd p Value 0.30 nd 0.22 0.94 nd 0.70 nd nd nd 95% CI of 0.094 nd 0.053 0.23 nd 0.30 nd nd nd OR Quart3 2.1 nd 1.9 5.0 nd 6.1 nd nd nd OR Quart 4 1.3 nd 1.1 1.8 nd 1.3 nd nd nd p Value 0.66 nd 0.91 0.42 nd 0.70 nd nd nd 95% CI of 0.36 nd 0.25 0.43 nd 0.30 nd nd nd OR Quart4 5.0 nd 4.8 7.8 nd 6.1 nd nd nd Carbonic anhydrase IX 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.00525 0.00780 0.00525 0.0170 nd nd Average 0.0125 0.0158 0.0125 0.0706 nd nd Stdev 0.0182 0.0196 0.0182 0.193 nd nd p(t-test) 0.51 0.020 nd nd Min 1.00E−9 0.000522 1.00E−9 0.00216 nd nd Max 0.119 0.0760 0.119 0.859 nd nd n (Samp) 62 19 62 19 nd nd n (Patient) 50 19 50 19 nd nd UO only Median 0.00432 0.0111 0.00432 0.0204 nd nd Average 0.0112 0.0178 0.0112 0.0693 nd nd Stdev 0.0189 0.0211 0.0189 0.188 nd nd p(t-test) 0.25 0.029 nd nd Min 1.00E−9 0.000522 1.00E−9 0.00216 nd nd Max 0.119 0.0760 0.119 0.859 nd nd n (Samp) 52 15 52 20 nd nd n (Patient) 41 15 41 20 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.54 nd 0.63 0.73 nd 0.81 nd nd nd SE 0.077 nd 0.085 0.072 nd 0.063 nd nd nd p 0.60 nd 0.12 0.0017 nd 8.1E−7 nd nd nd nCohort 1 62 nd 52 62 nd 52 nd nd nd nCohort 2 19 nd 15 19 nd 20 nd nd nd Cutoff 1 0.00269 nd 0.00444 0.0102 nd 0.0158 nd nd nd Sens 1 74% nd 73% 74% nd 70% nd nd nd Spec 1 26% nd 52% 61% nd 83% nd nd nd Cutoff 2 0.00187 nd 0.00269 0.00548 nd 0.0114 nd nd nd Sens 2 84% nd 80% 84% nd 80% nd nd nd Spec 2 15% nd 35% 52% nd 71% nd nd nd Cutoff 3 0.000712 nd 0.00105 0.00337 nd 0.00548 nd nd nd Sens 3 95% nd 93% 95% nd 90% nd nd nd Spec 3  6% nd 13% 32% nd 56% nd nd nd Cutoff 4 0.0121 nd 0.0114 0.0121 nd 0.0114 nd nd nd Sens 4 42% nd 47% 58% nd 80% nd nd nd Spec 4 71% nd 71% 71% nd 71% nd nd nd Cutoff 5 0.0183 nd 0.0143 0.0183 nd 0.0143 nd nd nd Sens 5 32% nd 47% 42% nd 75% nd nd nd Spec 5 81% nd 81% 81% nd 81% nd nd nd Cutoff 6 0.0293 nd 0.0212 0.0293 nd 0.0212 nd nd nd Sens 6 16% nd 20% 26% nd 50% nd nd nd Spec 6 90% nd 90% 90% nd 90% nd nd nd OR Quart 2 1.0 nd 1.5 3.4 nd 2.1 nd nd nd p Value 1.0 nd 0.68 0.31 nd 0.55 nd nd nd 95% CI of 0.21 nd 0.22 0.32 nd 0.18 nd nd nd OR Quart2 4.7 nd 10 35 nd 26 nd nd nd OR Quart 3 1.3 nd 1.5 10 nd 8.5 nd nd nd p Value 0.71 nd 0.68 0.039 nd 0.061 nd nd nd 95% CI of 0.30 nd 0.22 1.1 nd 0.90 nd nd nd OR Quart3 5.9 nd 10 93 nd 80 nd nd nd OR Quart 4 1.6 nd 4.9 12 nd 27 nd nd nd p Value 0.52 nd 0.078 0.028 nd 0.0039 nd nd nd 95% CI of 0.38 nd 0.84 1.3 nd 2.9 nd nd nd OR Quart4 6.8 nd 29 110 nd 250 nd nd nd Dipeptidyl peptidase IV 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 147 435 147 237 147 239 Average 7480 1090 7480 423 7480 852 Stdev 67000 2170 67000 468 67000 1110 p(t-test) 0.60 0.53 0.64 Min 0.200 0.899 0.200 3.65 0.200 2.62 Max 677000 11000 677000 1480 677000 4320 n (Samp) 102 31 102 36 102 22 n (Patient) 82 31 82 36 82 22 sCr only Median 266 147 266 130 266 96.7 Average 4260 927 4260 672 4260 1030 Stdev 47800 2100 47800 1270 47800 1670 p(t-test) 0.82 0.80 0.84 Min 0.200 6.52 0.200 18.2 0.200 10.1 Max 677000 7150 677000 4460 677000 4950 n (Samp) 201 11 201 12 201 9 n (Patient) 131 11 131 12 131 9 UO only Median 121 577 121 312 121 328 Average 536 1260 536 463 536 888 Stdev 1240 2270 1240 451 1240 1120 p(t-test) 0.030 0.74 0.24 Min 0.200 0.899 0.200 3.65 0.200 2.62 Max 9980 11000 9980 1410 9980 4320 n (Samp) 93 28 93 35 93 20 n (Patient) 71 28 71 35 71 20 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.57 0.48 0.63 0.53 0.49 0.60 0.61 0.53 0.65 SE 0.060 0.091 0.063 0.057 0.086 0.058 0.069 0.100 0.072 p 0.23 0.79 0.038 0.60 0.91 0.086 0.12 0.79 0.038 nCohort 1 102 201 93 102 201 93 102 201 93 nCohort 2 31 11 28 36 12 35 22 9 20 Cutoff 1 58.9 58.9 62.9 58.9 52.2 104 93.8 78.9 95.2 Sens 1 71% 73% 71% 72% 75% 71% 73% 78% 70% Spec 1 37% 32% 39% 37% 31% 49% 44% 35% 47% Cutoff 2 20.7 52.2 19.1 36.5 42.6 52.2 83.4 52.2 83.4 Sens 2 81% 82% 82% 81% 83% 80% 82% 89% 80% Spec 2 24% 31% 23% 29% 29% 35% 41% 31% 44% Cutoff 3 6.52 12.4 6.36 9.55 36.5 9.55 42.6 9.55 42.6 Sens 3 90% 91% 93% 92% 92% 91% 91% 100%  90% Spec 3 12% 15% 12% 15% 26% 15% 34% 13% 33% Cutoff 4 538 677 407 538 677 407 538 677 407 Sens 4 48% 27% 61% 33% 25% 40% 36% 33% 45% Spec 4 71% 70% 71% 71% 70% 71% 71% 70% 71% Cutoff 5 1110 1110 698 1110 1110 698 1110 1110 698 Sens 5 23% 18% 43% 11% 17% 26% 32% 33% 40% Spec 5 80% 80% 81% 80% 80% 81% 80% 80% 81% Cutoff 6 1960 1990 1560 1960 1990 1560 1960 1990 1560 Sens 6 13%  9% 18%  0%  8%  0% 14% 11% 25% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 0.83 1.0 0.23 1.9 1.0 0.66 4.2 5.3 2.8 p Value 0.76 1.0 0.088 0.29 0.98 0.52 0.089 0.13 0.24 95% CI of 0.24 0.14 0.044 0.59 0.14 0.19 0.80 0.60 0.50 OR Quart2 2.8 7.4 1.2 5.9 7.5 2.4 22 47 16 OR Quart 3 1.2 2.7 1.0 1.9 4.0 2.1 2.8 0 2.8 p Value 0.77 0.26 1.0 0.26 0.096 0.18 0.24 na 0.24 95% CI of 0.38 0.49 0.30 0.62 0.78 0.71 0.50 na 0.50 OR Quart3 3.8 14 3.3 6.1 20 6.5 16 na 16 OR Quart 4 1.5 1.0 2.1 1.9 0.50 1.9 5.0 3.1 5.0 p Value 0.44 1.0 0.20 0.29 0.58 0.27 0.054 0.34 0.058 95% CI of 0.51 0.14 0.68 0.59 0.044 0.62 0.98 0.31 0.95 OR Quart4 4.7 7.4 6.3 5.9 5.7 5.7 26 30 26

TABLE 2 Comparison of marker levels in urine samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0 or R) and in urine samples collected from subjects at 0, 24 hours, and 48 hours prior to reaching stage I or F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 1.75 3.29 1.75 0.538 1.75 0.362 Average 2.67 2.85 2.67 2.11 2.67 1.46 Stdev 2.47 2.38 2.47 2.56 2.47 1.95 p(t-test) 0.73 0.21 0.046 Min 0.00152 0.00181 0.00152 0.00212 0.00152 0.00546 Max 6.10 6.10 6.10 6.10 6.10 5.80 n (Samp) 421 25 421 33 421 17 n (Patient) 165 25 165 33 165 17 sCr only Median nd nd 1.47 3.95 1.47 0.763 Average nd nd 2.57 3.27 2.57 1.33 Stdev nd nd 2.45 2.75 2.45 1.42 p(t-test) nd nd 0.43 0.18 Min nd nd 0.00152 0.0843 0.00152 0.0324 Max nd nd 6.10 5.80 6.10 3.49 n (Samp) nd nd 511 8 511 7 n (Patient) nd nd 198 8 198 7 UO only Median 1.81 3.29 1.81 0.721 1.81 0.261 Average 2.73 2.89 2.73 1.92 2.73 1.84 Stdev 2.48 2.35 2.48 2.38 2.48 2.40 p(t-test) 0.74 0.093 0.15 Min 0.00152 0.00181 0.00152 0.00212 0.00152 0.00546 Max 6.10 6.10 6.10 6.10 6.10 5.80 n (Samp) 357 25 357 29 357 17 n (Patient) 135 25 135 29 135 17 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.52 nd 0.51 0.43 0.57 0.41 0.33 0.39 0.35 SE 0.060 nd 0.060 0.054 0.11 0.057 0.073 0.11 0.074 p 0.75 nd 0.84 0.21 0.48 0.11 0.024 0.35 0.040 nCohort 1 421 nd 357 421 511 357 421 511 357 nCohort 2 25 nd 25 33 8 29 17 7 17 Cutoff 1 0.363 nd 0.363 0.153 0.518 0.152 0.107 0.476 0.107 Sens 1 72% nd 72% 73% 75% 72% 71% 71% 71% Spec 1 33% nd 31% 22% 37% 19% 17% 36% 15% Cutoff 2 0.278 nd 0.278 0.0572 0.200 0.0497 0.0376 0.153 0.0351 Sens 2 80% nd 80% 82% 88% 83% 82% 86% 82% Spec 2 29% nd 27% 10% 26%  9%  7% 23%  7% Cutoff 3 0.0351 nd 0.0351 0.0319 0.0830 0.00312 0.0124 0.0319 0.0124 Sens 3 92% nd 92% 91% 100%  93% 94% 100%  94% Spec 3  7% nd  7%  6% 16%  1%  3%  7%  2% Cutoff 4 5.48 nd 5.57 5.48 5.13 5.57 5.48 5.13 5.57 Sens 4 24% nd 20% 30% 50% 24%  6%  0% 18% Spec 4 70% nd 70% 70% 70% 70% 70% 70% 70% Cutoff 5 5.80 nd 5.80 5.80 5.80 5.80 5.80 5.80 5.80 Sens 5 12% nd 12% 6%  0%  7%  0%  0%  0% Spec 5 94% nd 94% 94% 94% 94% 94% 94% 94% Cutoff 6 5.80 nd 5.80 5.80 5.80 5.80 5.80 5.80 5.80 Sens 6 12% nd 12%  6%  0%  7%  0%  0%  0% Spec 6 94% nd 94% 94% 94% 94% 94% 94% 94% OR Quart 2 1.8 nd 0.99 0.19 2.0 0.66 4.2 >2.0 2.1 p Value 0.37 nd 0.99 0.033 0.57 0.53 0.21 <0.56 0.41 95% CI of 0.51 nd 0.28 0.040 0.18 0.18 0.46 >0.18 0.37 OR Quart2 6.3 nd 3.5 0.88 22 2.4 38 na 12 OR Quart 3 2.6 nd 2.6 0.89 2.0 1.4 4.1 >3.1 1.5 p Value 0.11 nd 0.084 0.81 0.57 0.58 0.21 <0.33 0.65 95% CI of 0.80 nd 0.88 0.35 0.18 0.45 0.45 >0.32 0.25 OR Quart3 8.7 nd 7.7 2.3 22 4.1 37 na 9.3 OR Quart 4 0.99 nd 0.58 1.2 3.0 2.0 8.6 >2.0 4.3 p Value 0.99 nd 0.47 0.64 0.34 0.20 0.044 <0.56 0.069 95% CI of 0.24 nd 0.13 0.51 0.31 0.70 1.1 >0.18 0.89 OR Quart4 4.1 nd 2.5 3.0 29 5.5 70 na 21 C-X-C motif chemokine 2 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.485 1.87 0.485 6.90 0.485 0.889 Average 8.64 16.6 8.64 23.6 8.64 5.37 Stdev 24.6 39.6 24.6 44.3 24.6 7.31 p(t-test) 0.066 1.4E−4 0.48 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 20.9 n (Samp) 690 37 690 48 690 28 n (Patient) 279 37 279 48 279 28 sCr only Median 0.687 11.6 0.687 15.2 0.687 3.34 Average 8.64 42.0 8.64 33.1 8.64 10.1 Stdev 24.0 69.5 24.0 58.6 24.0 12.5 p(t-test) 6.6E−5 4.4E−4 0.83 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 31.3 n (Samp) 899 9 899 13 899 13 n (Patient) 335 9 335 13 335 13 UO only Median 0.671 1.65 0.671 6.97 0.671 2.64 Average 9.13 16.4 9.13 25.2 9.13 5.99 Stdev 24.9 40.7 24.9 46.4 24.9 7.43 p(t-test) 0.11 1.7E−4 0.53 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 20.9 n (Samp) 578 35 578 43 578 25 n (Patient) 205 35 205 43 205 25 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.58 0.72 0.55 0.68 0.73 0.68 0.52 0.58 0.55 SE 0.050 0.097 0.051 0.044 0.080 0.046 0.056 0.083 0.060 p 0.12 0.025 0.35 3.3E−5 0.0045 1.1E−4 0.73 0.34 0.38 nCohort 1 690 899 578 690 899 578 690 899 578 nCohort 2 37 9 35 48 13 43 28 13 25 Cutoff 1 0.00804 1.86 0.00804 1.45 5.86 1.45 0.00804 0.00804 0.00804 Sens 1 100%  78% 100%  71% 77% 72% 100%  100%  100%  Spec 1  0% 57%  0% 57% 73% 54%  0%  0%  0% Cutoff 2 0.00804 0.00804 0.00804 0.121 0.00804 0.299 0.00804 0.00804 0.00804 Sens 2 100%  100%  100%  81% 100%  81% 100%  100%  100%  Spec 2  0%  0%  0% 45%  0% 46%  0%  0%  0% Cutoff 3 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 0.00804 Sens 3 100%  100%  100%  100%  100%  100%  100%  100%  100%  Spec 3  0%  0%  0%  0%  0%  0%  0%  0%  0% Cutoff 4 4.12 4.66 4.76 4.12 4.66 4.76 4.12 4.66 4.76 Sens 4 38% 67% 34% 56% 77% 56% 36% 46% 40% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 8.05 8.68 8.50 8.05 8.68 8.50 8.05 8.68 8.50 Sens 5 32% 56% 29% 48% 62% 49% 29% 46% 28% Spec 5 80% 80% 80% 80% 80% 80% 80% 80% 80% Cutoff 6 19.6 19.7 21.7 19.6 19.7 21.7 19.6 19.7 21.7 Sens 6 16% 44% 14% 31% 46% 30%  4% 23%  0% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 0.16 0 >15 >14 0 >12 0.16 0 0.24 p Value 0.016 na <0.0087 <0.012 na <0.019 0.016 na 0.073 95% CI of 0.035 na >2.0 >1.8 na >1.5 0.034 na 0.050 OR Quart2 0.71 na na na na na 0.71 na 1.1 OR Quart 3 0.82 0.50 >11 >11 0.66 >12 0.48 0.39 0.99 p Value 0.65 0.57 <0.025 <0.025 0.66 <0.019 0.15 0.27 0.99 95% CI of 0.34 0.045 >1.4 >1.3 0.11 >1.5 0.18 0.076 0.36 OR Quart3 1.9 5.5 na na 4.0 na 1.3 2.1 2.7 OR Quart 4 1.1 3.1 >12 >29 2.7 >24 0.65 1.2 0.86 p Value 0.85 0.17 <0.019 <0.0011 0.14 <0.0020 0.35 0.76 0.78 95% CI of 0.48 0.61 >1.5 >3.9 0.71 >3.2 0.26 0.36 0.30 OR Quart4 2.4 15 na na 10 na 1.6 4.0 2.4 Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 343 669 343 1180 343 380 Average 808 1130 808 2210 808 1220 Stdev 1290 1140 1290 3740 1290 1780 p(t-test) 0.25 3.1E−5  0.23 Min 1.00E−9 18.7 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 9810 4050 9810 21100 9810 5550 n (Samp) 239 22 239 32 239 16 n (Patient) 157 22 157 32 157 16 sCr only Median nd nd 394 1010 394 2150 Average nd nd 954 1350 954 2600 Stdev nd nd 1740 1410 1740 2150 p(t-test) nd nd 0.58 0.014 Min nd nd 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max nd nd 21100 3390 21100 5380 n (Samp) nd nd 305 6 305 7 n (Patient) nd nd 184 6 184 7 UO only Median 346 699 346 1180 346 435 Average 847 1160 847 2270 847 1220 Stdev 1350 1120 1350 3900 1350 1790 p(t-test) 0.30 1.3E−4  0.31 Min 1.00E−9 18.7 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 9810 4050 9810 21100 9810 5550 n (Samp) 207 22 207 29 207 15 n (Patient) 130 22 130 29 130 15 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.64 nd 0.64 0.70 0.58 0.71 0.52 0.68 0.54 SE 0.066 nd 0.066 0.054 0.12 0.057 0.075 0.11 0.079 p 0.033 nd 0.030 1.6E−4 0.50 2.3E−4 0.82 0.10 0.63 nCohort 1 239 nd 207 239 305 207 239 305 207 nCohort 2 22 nd 22 32 6 29 16 7 15 Cutoff 1 337 nd 397 453 38.3 397 88.6 2070 134 Sens 1 73% nd 73% 72% 83% 72% 75% 71% 73% Spec 1 50% nd 55% 57% 16% 55% 24% 88% 28% Cutoff 2 266 nd 266 380 38.3 310 69.5 0 118 Sens 2 82% nd 82% 81% 83% 83% 81% 100%  80% Spec 2 44% nd 43% 52% 16% 48% 23%  0% 25% Cutoff 3 69.5 nd 69.5 96.1 0 125 0 0 69.5 Sens 3 91% nd 91% 91% 100%  93% 100%  100%  93% Spec 3 23% nd 21% 25%  0% 26%  0%  0% 21% Cutoff 4 730 nd 743 730 879 743 730 879 743 Sens 4 45% nd 45% 66% 50% 66% 38% 71% 33% Spec 4 70% nd 70% 70% 70% 70% 70% 70% 70% Cutoff 5 1280 nd 1410 1280 1590 1410 1280 1590 1410 Sens 5 32% nd 32% 47% 33% 45% 38% 71% 27% Spec 5 80% nd 80% 80% 80% 80% 80% 80% 80% Cutoff 6 2070 nd 2140 2070 2390 2140 2070 2390 2140 Sens 6 18% nd 18% 38% 33% 38% 19% 43% 13% Spec 6 90% nd 90% 90% 90% 90% 90% 90% 90% OR Quart 2 1.4 nd 1.0 0.73 0 1.4 0.57 0 1.3 p Value 0.70 nd 1.0 0.68 na 0.70 0.46 na 0.72 95% CI of 0.29 nd 0.19 0.16 na 0.29 0.13 na 0.28 OR Quart2 6.3 nd 5.2 3.4 na 6.3 2.5 na 6.3 OR Quart 3 2.5 nd 2.9 2.1 0.49 3.4 0.37 0 1.0 p Value 0.20 nd 0.13 0.25 0.56 0.081 0.25 na 1.0 95% CI of 0.62 nd 0.74 0.60 0.043 0.86 0.070 na 0.19 OR Quart3 10 nd 12 7.3 5.5 13 2.0 na 5.2 OR Quart 4 2.9 nd 2.9 5.2 1.5 5.3 1.2 2.6 1.7 p Value 0.14 nd 0.13 0.0047 0.66 0.013 0.77 0.26 0.48 95% CI of 0.72 nd 0.72 1.7 0.24 1.4 0.35 0.49 0.39 OR Quart4 11 nd 11 17 9.2 20 4.2 14 7.5 Cathepsin B 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.661 0.911 0.661 1.10 0.661 0.312 Average 2.94 1.16 2.94 5.27 2.94 1.34 Stdev 9.10 1.30 9.10 12.7 9.10 1.86 p(t-test) 0.36 0.19 0.48 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 78.1 5.47 78.1 64.9 78.1 4.98 n (Samp) 256 22 256 32 256 16 n (Patient) 163 22 163 32 163 16 sCr only Median nd nd 0.648 1.62 0.648 2.27 Average nd nd 2.81 6.92 2.81 5.45 Stdev nd nd 8.88 9.65 8.88 10.8 p(t-test) nd nd 0.26 0.44 Min nd nd 1.00E−9 0.593 1.00E−9 0.0682 Max nd nd 78.1 24.2 78.1 29.7 n (Samp) nd nd 322 6 322 7 n (Patient) nd nd 190 6 190 7 UO only Median 0.768 0.911 0.768 1.20 0.768 0.605 Average 3.26 1.14 3.26 5.03 3.26 2.90 Stdev 9.69 1.27 9.69 12.8 9.69 6.17 p(t-test) 0.31 0.38 0.89 Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 1.00E−9 Max 78.1 5.29 78.1 64.9 78.1 24.2 n (Samp) 222 22 222 29 222 15 n (Patient) 135 22 135 29 135 15 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.50 nd 0.47 0.62 0.73 0.59 0.42 0.60 0.44 SE 0.064 nd 0.066 0.056 0.12 0.059 0.077 0.11 0.079 p 0.96 nd 0.62 0.032 0.056 0.14 0.30 0.37 0.46 nCohort 1 256 nd 222 256 322 222 256 322 222 nCohort 2 22 nd 22 32 6 29 16 7 15 Cutoff 1 0.296 nd 0.296 0.572 0.797 0.522 0.0513 0.319 0.158 Sens 1 73% nd 73% 72% 83% 72% 75% 71% 73% Spec 1 32% nd 29% 48% 55% 39% 13% 34% 18% Cutoff 2 0.140 nd 0.140 0.463 0.797 0.460 0 0.309 0 Sens 2 82% nd 82% 81% 83% 83% 100%  86% 100%  Spec 2 19% nd 17% 40% 55% 35%  0% 33%  0% Cutoff 3 1.00E−9 nd 1.00E−9 0.290 0.572 0.236 0 0.0513 0 Sens 3 91% nd 91% 91% 100%  93% 100%  100%  100%  Spec 3 12% nd 10% 31% 48% 23%  0% 14%  0% Cutoff 4 1.46 nd 1.64 1.46 1.41 1.64 1.46 1.41 1.64 Sens 4 27% nd 23% 38% 50% 38% 31% 57% 33% Spec 4 70% nd 70% 70% 70% 70% 70% 70% 70% Cutoff 5 2.37 nd 2.74 2.37 2.37 2.74 2.37 2.37 2.74 Sens 5 14% nd  9% 25% 33% 28% 25% 43% 27% Spec 5 80% nd 80% 80% 80% 80% 80% 80% 80% Cutoff 6 5.61 nd 6.20 5.61 4.86 6.20 5.61 4.86 6.20 Sens 6  0% nd  0% 16% 33% 14%  0% 14%  7% Spec 6 90% nd 90% 90% 90% 90% 90% 90% 90% OR Quart 2 1.7 nd 3.3 2.9 >1.0 2.9 0.19 2.0 0 p Value 0.37 nd 0.082 0.13 <0.99 0.13 0.13 0.57 na 95% CI of 0.53 nd 0.86 0.73 >0.062 0.72 0.021 0.18 na OR Quart2 5.5 nd 13 11 na 11 1.7 23 na OR Quart 3 0.79 nd 1.7 3.7 >2.0 2.9 0.79 0 0.80 p Value 0.73 nd 0.47 0.054 <0.56 0.13 0.73 na 0.75 95% CI of 0.20 nd 0.39 0.98 >0.18 0.72 0.20 na 0.20 OR Quart3 3.1 nd 7.6 14 na 11 3.1 na 3.1 OR Quart 4 1.0 nd 1.7 4.1 >3.1 3.7 1.2 4.1 1.2 p Value 0.98 nd 0.47 0.035 <0.33 0.056 0.75 0.21 0.73 95% CI of 0.28 nd 0.39 1.1 >0.32 0.97 0.35 0.45 0.36 OR Quart4 3.7 nd 7.6 16 na 14 4.2 38 4.3 Dipeptidyl peptidase IV 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 157 473 157 662 157 455 Average 4080 1160 4080 1750 4080 758 Stdev 47500 1640 47500 3170 47500 826 p(t-test) 0.81 0.83 0.82 Min 0.200 7.95 0.200 10.1 0.200 17.0 Max 677000 5420 677000 12500 677000 2280 n (Samp) 203 16 203 19 203 11 n (Patient) 135 16 135 19 135 11 UO only Median 151 603 151 639 151 556 Average 619 1230 619 1480 619 836 Stdev 1350 1630 1350 2970 1350 777 p(t-test) 0.091 0.028 0.60 Min 0.200 7.95 0.200 10.1 0.200 17.0 Max 11000 5420 11000 12500 11000 2280 n (Samp) 174 16 174 18 174 11 n (Patient) 114 16 114 18 114 11 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.61 nd 0.63 0.66 nd 0.65 0.61 nd 0.68 SE 0.077 nd 0.078 0.071 nd 0.073 0.093 nd 0.092 p 0.14 nd 0.086 0.028 nd 0.039 0.24 nd 0.055 nCohort 1 203 nd 174 203 nd 174 203 nd 174 nCohort 2 16 nd 16 19 nd 18 11 nd 11 Cutoff 1 63.4 nd 52.3 294 nd 294 161 nd 407 Sens 1 75% nd 75% 74% nd 72% 73% nd 73% Spec 1 33% nd 32% 60% nd 61% 51% nd 65% Cutoff 2 52.3 nd 31.7 48.0 nd 48.0 52.3 nd 161 Sens 2 81% nd 81% 84% nd 83% 82% nd 82% Spec 2 31% nd 25% 29% nd 29% 31% nd 52% Cutoff 3 18.2 nd 18.2 18.2 nd 18.2 39.0 nd 39.0 Sens 3 94% nd 94% 95% nd 94% 91% nd 91% Spec 3 19% nd 20% 19% nd 20% 27% nd 27% Cutoff 4 560 nd 529 560 nd 529 560 nd 529 Sens 4 44% nd 50% 58% nd 61% 36% nd 55% Spec 4 70% nd 70% 70% nd 70% 70% nd 70% Cutoff 5 1010 nd 889 1010 nd 889 1010 nd 889 Sens 5 25% nd 31% 26% nd 33% 36% nd 36% Spec 5 80% nd 80% 80% nd 80% 80% nd 80% Cutoff 6 1560 nd 1530 1560 nd 1530 1560 nd 1530 Sens 6 25% nd 31% 16% nd 11% 18% nd 18% Spec 6 90% nd 90% 90% nd 90% 90% nd 90% OR Quart 2 0.64 nd 0.64 0.64 nd 0.65 3.1 nd 1.0 p Value 0.63 nd 0.63 0.63 nd 0.65 0.34 nd 1.0 95% CI of 0.10 nd 0.10 0.10 nd 0.10 0.31 nd 0.061 OR Quart2 4.0 nd 4.0 4.0 nd 4.1 30 nd 16 OR Quart 3 2.1 nd 1.4 2.5 nd 1.7 3.1 nd 4.3 p Value 0.32 nd 0.70 0.20 nd 0.46 0.33 nd 0.20 95% CI of 0.49 nd 0.29 0.62 nd 0.39 0.31 nd 0.46 OR Quart3 8.8 nd 6.5 10 nd 7.7 31 nd 40 OR Quart 4 1.7 nd 2.5 2.5 nd 3.0 4.2 nd 5.4 p Value 0.48 nd 0.20 0.21 nd 0.12 0.21 nd 0.13 95% CI of 0.39 nd 0.61 0.61 nd 0.74 0.45 nd 0.60 OR Quart4 7.5 nd 10 10 nd 12 39 nd 48

TABLE 3 Comparison of the maximum marker levels in urine samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0) and the maximum values in urine samples collected from subjects between enrollment and 0, 24 hours, and 48 hours prior to reaching stage F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 4.78 2.99 4.78 3.49 4.78 2.99 Average 3.59 2.92 3.59 3.09 3.59 2.83 Stdev 2.43 2.66 2.43 2.64 2.43 2.50 p(t-test) 0.31 0.46 0.40 Min 0.00270 0.00133 0.00270 0.00133 0.00270 0.0324 Max 6.10 5.80 6.10 5.80 6.10 5.80 n (Samp) 103 16 103 15 103 8 n (Patient) 103 16 103 15 103 8 sCr only Median 4.50 5.24 4.50 5.16 nd nd Average 3.52 3.82 3.52 3.80 nd nd Stdev 2.47 2.57 2.47 2.55 nd nd p(t-test) 0.74 0.75 nd nd Min 0.00270 0.00133 0.00270 0.00133 nd nd Max 6.10 5.80 6.10 5.80 nd nd n (Samp) 170 8 170 8 nd nd n (Patient) 170 8 170 8 nd nd UO only Median 4.20 0.348 4.20 0.480 4.20 1.83 Average 3.52 2.21 3.52 2.43 3.52 2.57 Stdev 2.42 2.68 2.42 2.74 2.42 2.82 p(t-test) 0.11 0.21 0.36 Min 0.00270 0.0324 0.00270 0.0324 0.00270 0.0324 Max 6.10 5.80 6.10 5.80 6.10 5.80 n (Samp) 87 10 87 9 87 6 n (Patient) 87 10 87 9 87 6 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.41 0.49 0.32 0.41 0.47 0.35 0.38 nd 0.36 SE 0.080 0.11 0.098 0.082 0.11 0.10 0.11 nd 0.13 p 0.24 0.95 0.073 0.29 0.81 0.14 0.28 nd 0.25 nCohort 1 103 170 87 103 170 87 103 nd 87 nCohort 2 16 8 10 15 8 9 8 nd 6 Cutoff 1 0.170 2.39 0.170 0.170 2.39 0.152 0.170 nd 0.0851 Sens 1 75% 75% 70% 73% 75% 78%  75% nd 83%  Spec 1 13% 38% 10% 13% 38% 9% 13% nd 9% Cutoff 2 0.152 0.152 0.152 0.152 0.152 0.0851 0.0851 nd 0.0851 Sens 2 81% 88% 80% 80% 88% 89%  88% nd 83%  Spec 2 12% 13%  9% 12% 13% 9% 12% nd 9% Cutoff 3 0.0319 0 0.0851 0.0319 0 0.0273 0.0319 nd 0.0273 Sens 3 94% 100%  90% 93% 100%  100%  100%  nd 100%  Spec 3  6%  0%  9%  6%  0% 5%  6% nd 5% Cutoff 4 5.80 5.80 5.80 5.80 5.80 5.80 5.80 nd 5.80 Sens 4  0%  0%  0%  0%  0% 0%  0% nd 0% Spec 4 89% 88% 86% 89% 88% 86%  89% nd 86%  Cutoff 5 5.80 5.80 5.80 5.80 5.80 5.80 5.80 nd 5.80 Sens 5  0%  0%  0%  0%  0% 0%  0% nd 0% Spec 5 89% 88% 86% 89% 88% 86%  89% nd 86%  Cutoff 6 5.84 6.10 6.10 5.84 6.10 6.10 5.84 nd 6.10 Sens 6  0%  0%  0%  0%  0% 0%  0% nd 0% Spec 6 90% 100%  100%  90% 100%  100%  90% nd 100%  OR Quart 2 >9.1 >5.8 >3.6 >9.5 >5.8 >3.4 >3.4 nd 1.0 p Value <0.045 <0.12 <0.29 <0.041 <0.12 <0.30 <0.31 nd 0.98 95% CI of >1.0 >0.65 >0.35 >1.1 >0.65 >0.33 >0.33 nd 0.062 OR Quart2 na na na na na na na nd 18 OR Quart 3 >2.1 >1.0 >1.1 >2.1 >1.0 >1.0 >2.2 nd 1.0 p Value <0.54 <0.99 <0.95 <0.54 <0.99 <0.98 <0.54 nd 0.98 95% CI of >0.18 >0.062 >0.064 >0.18 >0.062 >0.062 >0.18 nd 0.062 OR Quart3 na na na na na na na nd 18 OR Quart 4 >9.5 >2.1 >8.3 >7.8 >2.1 >6.3 >3.5 nd 3.4 p Value <0.041 <0.54 <0.059 <0.065 <0.54 <0.11 <0.29 nd 0.30 95% CI of >1.1 >0.19 >0.92 >0.88 >0.19 >0.68 >0.34 nd 0.33 OR Quart4 na na na na na na na nd 36 C-X-C motif chemokine 2 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 1.04 28.7 1.04 27.8 1.04 3.34 Average 9.16 42.4 9.16 37.7 9.16 12.4 Stdev 30.2 57.0 30.2 56.5 30.2 14.7 p(t-test) 2.7E−5 2.9E−4 0.73 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 36.2 n (Samp) 190 21 190 21 190 11 n (Patient) 190 21 190 21 190 11 sCr only Median 1.90 27.8 1.90 27.8 1.90 6.02 Average 13.1 38.9 13.1 38.9 13.1 11.5 Stdev 33.8 63.2 33.8 63.2 33.8 13.5 p(t-test) 0.017 0.017 0.91 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.135 Max 266 217 266 217 266 31.3 n (Samp) 295 11 295 11 295 6 n (Patient) 295 11 295 11 295 6 UO only Median 1.60 35.3 1.60 29.0 1.60 3.34 Average 9.22 53.2 9.22 46.6 9.22 14.0 Stdev 29.8 64.3 29.8 64.7 29.8 15.7 p(t-test) 6.7E−6 1.2E−4 0.64 Min 0.00804 0.534 0.00804 0.534 0.00804 0.0260 Max 266 217 266 217 266 36.2 n (Samp) 134 15 134 15 134 9 n (Patient) 134 15 134 15 134 9 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.79 0.70 0.81 0.79 0.70 0.80 0.68 0.65 0.67 SE 0.061 0.089 0.070 0.061 0.089 0.070 0.091 0.12 0.10 p 1.9E−6 0.022 1.0E−5 2.7E−6 0.023 1.5E−5 0.042 0.23 0.089 nCohort 1 190 295 134 190 295 134 190 295 134 nCohort 2 21 11 15 21 11 15 11 6 9 Cutoff 1 3.33 1.95 3.33 3.33 1.95 3.33 1.52 0.570 1.52 Sens 1 71% 73% 73% 71% 73% 73% 73% 83% 78% Spec 1 65% 51% 60% 65% 51% 60% 54% 41% 49% Cutoff 2 1.52 0.570 1.95 1.52 0.570 1.95 0.541 0.570 0.544 Sens 2 81% 82% 80% 81% 82% 80% 82% 83% 89% Spec 2 54% 41% 56% 54% 41% 56% 48% 41% 45% Cutoff 3 0.371 0.134 0.544 0.371 0.134 0.544 0.134 0.134 0.00804 Sens 3 90% 91% 93% 90% 91% 93% 91% 100%  100%  Spec 3 48% 37% 45% 48% 37% 45% 45% 37%  1% Cutoff 4 4.12 6.43 4.69 4.12 6.43 4.69 4.12 6.43 4.69 Sens 4 67% 64% 67% 67% 55% 67% 45% 50% 44% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 6.66 11.6 8.08 6.66 11.6 8.08 6.66 11.6 8.08 Sens 5 62% 55% 67% 62% 55% 67% 45% 33% 44% Spec 5 80% 80% 81% 80% 80% 81% 80% 80% 81% Cutoff 6 14.8 28.5 14.8 14.8 28.5 14.8 14.8 28.5 14.8 Sens 6 57% 45% 60% 57% 45% 60% 36% 17% 44% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 >4.2 2.0 >3.3 >4.2 2.0 >3.3 >3.2 >2.1 >3.2 p Value <0.20 0.57 <0.32 <0.20 0.57 <0.32 <0.32 <0.56 <0.33 95% CI of >0.46 0.18 >0.32 >0.46 0.18 >0.32 >0.32 >0.18 >0.31 OR Quart2 na 23 na na 23 na na na na OR Quart 3 >4.2 2.0 >2.1 >4.2 2.0 >2.1 >3.2 >1.0 >2.1 p Value <0.20 0.57 <0.55 <0.20 0.57 <0.55 <0.32 <0.99 <0.56 95% CI of >0.46 0.18 >0.18 >0.46 0.18 >0.18 >0.32 >0.062 >0.18 OR Quart3 na 23 na na 23 na na na na OR Quart 4 >17 6.3 >13 >17 6.3 >13 >5.4 >3.1 >4.4 p Value <0.0076 0.091 <0.017 <0.0076 0.091 <0.017 <0.13 <0.33 <0.20 95% CI of >2.1 0.74 >1.6 >2.1 0.74 >1.6 >0.61 >0.31 >0.46 OR Quart4 na 54 na na 54 na na na na Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 382 3580 382 3580 382 2150 Average 828 5520 828 4430 828 2820 Stdev 1360 6880 1360 5560 1360 1670 p(t-test) 2.4E−8 4.5E−7 3.6E−4 Min 1.00E−9 99.0 1.00E−9 99.0 1.00E−9 326 Max 9810 21100 9810 21100 9810 5370 n (Samp) 98 12 98 12 98 7 n (Patient) 98 12 98 12 98 7 sCr only Median 494 3030 494 3030 nd nd Average 1230 5100 1230 5100 nd nd Stdev 2230 6800 2230 6800 nd nd p(t-test) 2.6E−4 2.6E−4 nd nd Min 1.00E−9 99.0 1.00E−9 99.0 nd nd Max 21100 18400 21100 18400 nd nd n (Samp) 159 6 159 6 nd nd n (Patient) 159 6 159 6 nd nd UO only Median 371 4150 371 4150 371 2930 Average 873 7420 873 5790 873 2930 Stdev 1480 7810 1480 6420 1480 1810 p(t-test) 1.5E−9 1.1E−7 0.0016 Min 1.00E−9 326 1.00E−9 326 1.00E−9 326 Max 9810 21100 9810 21100 9810 5370 n (Samp) 82 8 82 8 82 6 n (Patient) 82 8 82 8 82 6 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.84 0.75 0.90 0.84 0.75 0.90 0.87 nd 0.85 SE 0.073 0.12 0.074 0.074 0.12 0.075 0.088 nd 0.10 p 3.6E−6 0.030 7.6E−8 4.4E−6 0.030 1.4E−7 2.9E−5 nd 5.0E−4 nCohort 1 98 159 82 98 159 82 98 nd 82 nCohort 2 12 6 8 12 6 8 7 nd 6 Cutoff 1 2070 606 3280 2070 606 3280 2070 nd 1840 Sens 1 75% 83% 75% 75% 83% 75% 71% nd 83% Spec 1 91% 58% 95% 91% 58% 95% 91% nd 87% Cutoff 2 606 606 2070 606 606 2070 1990 nd 1840 Sens 2 83% 83% 88% 83% 83% 88% 86% nd 83% Spec 2 68% 58% 89% 68% 58% 89% 89% nd 87% Cutoff 3 310 88.6 310 310 88.6 310 310 nd 310 Sens 3 92% 100%  100%  92% 100%  100%  100%  nd 100%  Spec 3 45% 18% 46% 45% 18% 46% 45% nd 46% Cutoff 4 730 1150 695 730 1150 695 730 nd 695 Sens 4 75% 67% 88% 75% 67% 88% 86% nd 83% Spec 4 70% 70% 71% 70% 70% 71% 70% nd 71% Cutoff 5 1280 1840 1280 1280 1840 1280 1280 nd 1280 Sens 5 75% 67% 88% 75% 67% 88% 86% nd 83% Spec 5 81% 81% 80% 81% 81% 80% 81% nd 80% Cutoff 6 2070 3280 2140 2070 3280 2140 2070 nd 2140 Sens 6 75% 50% 75% 75% 50% 75% 71% nd 50% Spec 6 91% 91% 90% 91% 91% 90% 91% nd 90% OR Quart 2 0.96 0 >1.0 0.96 0 >1.0 >1.0 nd >1.0 p Value 0.98 na <1.0 0.98 na <1.0 <0.98 nd <0.97 95% CI of 0.057 na >0.059 0.057 na >0.059 >0.062 nd >0.061 OR Quart2 16 na na 16 na na na nd na OR Quart 3 1.0 1.0 >0 1.0 1.0 >0 >0 nd >0 p Value 1.0 1.0 <na   1.0 1.0 <na   <na   nd <na   95% CI of 0.059 0.060 >na   0.059 0.060 >na   >na   nd >na   OR Quart3 17 17 na 17 17 na na nd na OR Quart 4 12 4.2 >9.6 12 4.2 >9.6 >7.4 nd >6.5 p Value 0.022 0.21 <0.043 0.022 0.21 <0.043 <0.073 nd <0.10 95% CI of 1.4 0.45 >1.1 1.4 0.45 >1.1 >0.83 nd >0.69 OR Quart4 110 39 na 110 39 na na nd na Cathepsin B 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.556 4.74 0.556 4.74 0.556 2.27 Average 2.13 12.7 2.13 12.7 2.13 2.62 Stdev 7.41 19.1 7.41 19.1 7.41 2.21 p(t-test) 2.7E−4 2.7E−4 0.86 Min 1.00E−9 0.310 1.00E−9 0.310 1.00E−9 0.310 Max 72.4 64.9 72.4 64.9 72.4 6.19 n (Samp) 102 12 102 12 102 7 n (Patient) 102 12 102 12 102 7 sCr only Median 0.897 9.47 0.897 9.47 nd nd Average 3.16 12.6 3.16 12.6 nd nd Stdev 9.92 12.0 9.92 12.0 nd nd p(t-test) 0.025 0.025 nd nd Min 1.00E−9 0.405 1.00E−9 0.405 nd nd Max 78.1 29.7 78.1 29.7 nd nd n (Samp) 162 6 162 6 nd nd n (Patient) 162 6 162 6 nd nd UO only Median 0.677 4.74 0.677 4.74 0.677 2.13 Average 2.26 14.2 2.26 14.2 2.26 2.68 Stdev 7.97 22.7 7.97 22.7 7.97 2.42 p(t-test) 0.0015 0.0015 0.90 Min 1.00E−9 0.310 1.00E−9 0.310 1.00E−9 0.310 Max 72.4 64.9 72.4 64.9 72.4 6.19 n (Samp) 87 8 87 8 87 6 n (Patient) 87 8 87 8 87 6 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.79 0.82 0.77 0.79 0.82 0.77 0.71 nd 0.69 SE 0.081 0.11 0.10 0.081 0.11 0.10 0.11 nd 0.12 p 4.2E−4 0.0030 0.0064 4.2E−4 0.0030 0.0064 0.059 nd 0.13 nCohort 1 102 162 87 102 162 87 102 nd 87 nCohort 2 12 6 8 12 6 8 7 nd 6 Cutoff 1 0.949 2.16 0.949 0.949 2.16 0.949 0.888 nd 0.604 Sens 1 75% 83% 75% 75% 83% 75% 71% nd 83% Spec 1 58% 77% 56% 58% 77% 56% 58% nd 49% Cutoff 2 0.888 2.16 0.888 0.888 2.16 0.888 0.604 nd 0.604 Sens 2 83% 83% 88% 83% 83% 88% 86% nd 83% Spec 2 58% 77% 56% 58% 77% 56% 53% nd 49% Cutoff 3 0.397 0.397 0.309 0.397 0.397 0.309 0.309 nd 0.309 Sens 3 92% 100%  100%  92% 100%  100%  100%  nd 100%  Spec 3 40% 31% 31% 40% 31% 31% 32% nd 31% Cutoff 4 1.42 1.67 1.49 1.42 1.67 1.49 1.42 nd 1.49 Sens 4 67% 83% 62% 67% 83% 62% 57% nd 50% Spec 4 71% 70% 70% 71% 70% 70% 71% nd 70% Cutoff 5 2.04 2.74 2.04 2.04 2.74 2.04 2.04 nd 2.04 Sens 5 67% 67% 62% 67% 67% 62% 57% nd 50% Spec 5 80% 80% 80% 80% 80% 80% 80% nd 80% Cutoff 6 3.88 5.61 3.76 3.88 5.61 3.76 3.88 nd 3.76 Sens 6 50% 67% 50% 50% 67% 50% 29% nd 33% Spec 6 90% 90% 91% 90% 90% 91% 90% nd 91% OR Quart 2 >2.1 >1.0 >1.0 >2.1 >1.0 >1.0 >1.0 nd >2.2 p Value <0.56 <0.99 <1.0 <0.56 <0.99 <1.0 <0.98 nd <0.53 95% CI of >0.18 >0.062 >0.059 >0.18 >0.062 >0.059 >0.062 nd >0.18 OR Quart2 na na na na na na na nd na OR Quart 3 >2.2 >1.0 >2.1 >2.2 >1.0 >2.1 >2.2 nd >1.0 p Value <0.54 <0.99 <0.56 <0.54 <0.99 <0.56 <0.54 nd <0.98 95% CI of >0.18 >0.062 >0.18 >0.18 >0.062 >0.18 >0.18 nd >0.062 OR Quart3 na na na na na na na nd na OR Quart 4 >11 >4.4 >6.1 >11 >4.4 >6.1 >4.5 nd >3.3 p Value <0.031 <0.19 <0.11 <0.031 <0.19 <0.11 <0.19 nd <0.32 95% CI of >1.2 >0.47 >0.65 >1.2 >0.47 >0.65 >0.47 nd >0.32 OR Quart4 na na na na na na na nd na Dipeptidyl peptidase IV 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 143 2270 143 2270 143 2270 Average 9210 2860 9210 2860 9210 2490 Stdev 74700 2490 74700 2490 74700 2330 p(t-test) 0.79 0.79 0.83 Min 0.200 0.651 0.200 0.651 0.200 10.1 Max 677000 7150 677000 7150 677000 5420 n (Samp) 82 10 82 10 82 6 n (Patient) 82 10 82 10 82 6 UO only Median 103 2270 103 2270 nd nd Average 604 2720 604 2720 nd nd Stdev 1400 2100 1400 2100 nd nd p(t-test) 1.0E−3 1.0E−3 nd nd Min 0.200 10.1 0.200 10.1 nd nd Max 9980 5420 9980 5420 nd nd n (Samp) 71 6 71 6 nd nd n (Patient) 71 6 71 6 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.74 nd 0.81 0.74 nd 0.81 0.68 nd nd SE 0.094 nd 0.11 0.094 nd 0.11 0.12 nd nd p 0.012 nd 0.0037 0.012 nd 0.0037 0.15 nd nd nCohort 1 82 nd 71 82 nd 71 82 nd nd nCohort 2 10 nd 6 10 nd 6 6 nd nd Cutoff 1 1210 nd 1190 1210 nd 1190 12.4 nd nd Sens 1 70% nd 83% 70% nd 83% 83% nd nd Spec 1 82% nd 86% 82% nd 86% 18% nd nd Cutoff 2 659 nd 1190 659 nd 1190 12.4 nd nd Sens 2 80% nd 83% 80% nd 83% 83% nd nd Spec 2 73% nd 86% 73% nd 86% 18% nd nd Cutoff 3 9.55 nd 9.55 9.55 nd 9.55 9.55 nd nd Sens 3 90% nd 100%  90% nd 100%  100%  nd nd Spec 3 15% nd 17% 15% nd 17% 15% nd nd Cutoff 4 545 nd 407 545 nd 407 545 nd nd Sens 4 80% nd 83% 80% nd 83% 67% nd nd Spec 4 71% nd 70% 71% nd 70% 71% nd nd Cutoff 5 1190 nd 942 1190 nd 942 1190 nd nd Sens 5 70% nd 83% 70% nd 83% 67% nd nd Spec 5 80% nd 80% 80% nd 80% 80% nd nd Cutoff 6 2020 nd 1810 2020 nd 1810 2020 nd nd Sens 6 50% nd 67% 50% nd 67% 50% nd nd Spec 6 90% nd 90% 90% nd 90% 90% nd nd OR Quart 2 0 nd 0 0 nd 0 0 nd nd p Value na nd na na nd na na nd nd 95% CI of na nd na na nd na na nd nd OR Quart2 na nd na na nd na na nd nd OR Quart 3 0.48 nd 0 0.48 nd 0 0 nd nd p Value 0.56 nd na 0.56 nd na na nd nd 95% CI of 0.040 nd na 0.040 nd na na nd nd OR Quart3 5.7 nd na 5.7 nd na na nd nd OR Quart 4 4.6 nd 6.0 4.6 nd 6.0 2.2 nd nd p Value 0.079 nd 0.12 0.079 nd 0.12 0.39 nd nd 95% CI of 0.84 nd 0.63 0.84 nd 0.63 0.36 nd nd OR Quart4 25 nd 57 25 nd 57 14 nd nd

TABLE 4 Comparison of marker levels in EDTA samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0) and in EDTA samples collected from subjects at 0, 24 hours, and 48 hours prior to reaching stage R, I or F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 2.38 2.60 2.38 2.37 2.38 2.46 Average 2.90 3.66 2.90 3.86 2.90 3.17 Stdev 1.90 3.11 1.90 3.82 1.90 2.08 p(t-test) 0.020 0.0058 0.49 Min 0.850 0.759 0.850 1.14 0.850 1.04 Max 12.1 16.2 12.1 22.7 12.1 9.51 n (Samp) 263 51 263 56 263 26 n (Patient) 111 51 111 56 111 26 sCr only Median 2.38 4.85 2.38 4.23 2.38 4.37 Average 2.98 5.96 2.98 5.76 2.98 4.24 Stdev 2.03 4.33 2.03 5.04 2.03 2.01 p(t-test) 1.4E−8 3.7E−8 0.027 Min 0.729 0.759 0.729 1.51 0.729 1.54 Max 16.7 16.2 16.7 22.7 16.7 7.60 n (Samp) 466 18 466 21 466 13 n (Patient) 180 18 180 21 180 13 UO only Median 2.46 3.00 2.46 2.54 2.46 2.45 Average 2.96 3.80 2.96 3.78 2.96 3.41 Stdev 1.87 2.87 1.87 3.19 1.87 3.29 p(t-test) 0.011 0.016 0.32 Min 0.899 1.00 0.899 1.14 0.899 1.04 Max 12.1 14.6 12.1 16.5 12.1 16.2 n (Samp) 221 50 221 52 221 23 n (Patient) 91 50 91 52 91 23 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.57 0.74 0.59 0.55 0.72 0.55 0.55 0.71 0.52 SE 0.045 0.068 0.046 0.043 0.064 0.045 0.061 0.082 0.064 p 0.14 4.4E−4 0.051 0.24 7.0E−4 0.22 0.45 0.0093 0.81 nCohort 1 263 466 221 263 466 221 263 466 221 nCohort 2 51 18 50 56 21 52 26 13 23 Cutoff 1 1.93 2.86 2.08 1.80 2.73 1.88 2.10 2.45 1.66 Sens 1 71% 72% 70% 71% 71% 71% 73% 77% 74% Spec 1 37% 62% 38% 32% 60% 33% 41% 52% 27% Cutoff 2 1.70 2.13 1.74 1.62 1.88 1.62 1.59 2.19 1.54 Sens 2 82% 83% 80% 80% 81% 81% 81% 85% 83% Spec 2 29% 42% 29% 26% 33% 26% 25% 44% 23% Cutoff 3 1.40 1.70 1.59 1.46 1.76 1.43 1.37 1.88 1.37 Sens 3 90% 94% 90% 91% 90% 90% 92% 92% 91% Spec 3 19% 27% 25% 20% 30% 19% 18% 33% 19% Cutoff 4 3.23 3.27 3.43 3.23 3.27 3.43 3.23 3.27 3.43 Sens 4 37% 67% 40% 32% 67% 35% 35% 62% 35% Spec 4 70% 70% 71% 70% 70% 71% 70% 70% 71% Cutoff 5 3.85 4.11 4.15 3.85 4.11 4.15 3.85 4.11 4.15 Sens 5 29% 61% 28% 29% 57% 27% 23% 62% 13% Spec 5 80% 80% 80% 80% 80% 80% 80% 80% 80% Cutoff 6 5.37 5.50 5.50 5.37 5.50 5.50 5.37 5.50 5.50 Sens 6 18% 44% 16% 18% 29% 19% 12% 23%  9% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 2.4 3.1 1.8 1.7 1.5 1.3 1.2 2.0 1.5 p Value 0.077 0.34 0.23 0.23 0.66 0.51 0.75 0.57 0.54 95% CI of 0.91 0.31 0.68 0.73 0.25 0.56 0.35 0.18 0.43 OR Quart2 6.2 30 5.0 3.8 9.1 3.2 4.2 22 4.9 OR Quart 3 2.0 2.0 2.4 0.99 0.99 0.89 1.2 2.0 1.0 p Value 0.16 0.57 0.073 0.97 0.99 0.81 0.75 0.57 1.0 95% CI of 0.76 0.18 0.92 0.40 0.14 0.35 0.35 0.18 0.27 OR Quart3 5.4 23 6.4 2.4 7.2 2.3 4.2 22 3.6 OR Quart 4 2.6 13 2.6 1.7 7.7 1.7 1.9 8.4 1.2 p Value 0.051 0.014 0.048 0.23 0.0078 0.22 0.28 0.046 0.75 95% CI of 1.00 1.7 1.0 0.73 1.7 0.73 0.60 1.0 0.35 OR Quart4 6.7 100 6.9 3.8 35 3.9 5.9 68 4.2 Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 3630 3850 3630 3360 3630 4440 Average 3940 4030 3940 4520 3940 4580 Stdev 1330 1360 1330 4260 1330 2250 p(t-test) 0.81 0.37 0.26 Min 1700 1120 1700 2100 1700 1870 Max 7950 6070 7950 23300 7950 8860 n (Samp) 55 16 55 24 55 8 n (Patient) 54 16 54 24 54 8 UO only Median 4180 3800 4180 3360 4180 4410 Average 4290 4040 4290 4510 4290 3960 Stdev 1610 1490 1610 4260 1610 1550 p(t-test) 0.61 0.75 0.62 Min 1700 1120 1700 2100 1700 1870 Max 9230 6070 9230 23300 9230 6200 n (Samp) 49 14 49 24 49 7 n (Patient) 45 14 45 24 45 7 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.55 nd 0.48 0.46 nd 0.41 0.60 nd 0.49 SE 0.084 nd 0.089 0.072 nd 0.073 0.11 nd 0.12 p 0.57 nd 0.79 0.54 nd 0.24 0.36 nd 0.91 nCohort 1 55 nd 49 55 nd 49 55 nd 49 nCohort 2 16 nd 14 24 nd 24 8 nd 7 Cutoff 1 3490 nd 3310 2630 nd 2630 3630 nd 3630 Sens 1 75% nd 71% 71% nd 71% 75% nd 71% Spec 1 45% nd 33% 11% nd 12% 51% nd 37% Cutoff 2 2770 nd 2510 2110 nd 2110 1900 nd 1900 Sens 2 81% nd 86% 83% nd 83% 88% nd 86% Spec 2 13% nd 12% 5% nd  6%  5% nd  6% Cutoff 3 2240 nd 2240 2100 nd 2100 1840 nd 1840 Sens 3 94% nd 93% 92% nd 92% 100%  nd 100%  Spec 3  9% nd 10%  5% nd  6%  4% nd  4% Cutoff 4 4320 nd 4690 4320 nd 4690 4320 nd 4690 Sens 4 44% nd 36% 38% nd 29% 62% nd 29% Spec 4 71% nd 71% 71% nd 71% 71% nd 71% Cutoff 5 4690 nd 5460 4690 nd 5460 4690 nd 5460 Sens 5 38% nd 29% 29% nd 21% 38% nd 14% Spec 5 80% nd 82% 80% nd 82% 80% nd 82% Cutoff 6 5580 nd 6490 5580 nd 6490 5580 nd 6490 Sens 6 12% nd  0% 17% nd  4% 25% nd  0% Spec 6 91% nd 92% 91% nd 92% 91% nd 92% OR Quart 2 0.65 nd 0.43 0.17 nd 0.43 0.43 nd 1.0 p Value 0.61 nd 0.37 0.040 nd 0.30 0.51 nd 1.0 95% CI of 0.12 nd 0.066 0.030 nd 0.090 0.035 nd 0.12 OR Quart2 3.5 nd 2.8 0.92 nd 2.1 5.3 nd 8.3 OR Quart 3 0.65 nd 1.0 0.64 nd 0.83 0.93 nd 0.46 p Value 0.61 nd 1.0 0.51 nd 0.80 0.94 nd 0.55 95% CI of 0.12 nd 0.20 0.17 nd 0.20 0.11 nd 0.037 OR Quart3 3.5 nd 5.0 2.4 nd 3.4 7.6 nd 5.8 OR Quart 4 1.6 nd 1.1 1.1 nd 2.7 1.5 nd 1.0 p Value 0.52 nd 0.92 0.89 nd 0.15 0.68 nd 1.0 95% CI of 0.37 nd 0.22 0.30 nd 0.71 0.21 nd 0.12 OR Quart4 7.2 nd 5.5 3.9 nd 10 11 nd 8.3 Neprilysin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.689 0.927 0.689 0.827 0.689 0.605 Average 1.18 1.27 1.18 1.20 1.18 0.816 Stdev 1.12 0.993 1.12 1.10 1.12 0.785 p(t-test) 0.76 0.93 0.38 Min 0.0870 0.183 0.0870 0.191 0.0870 0.244 Max 4.92 3.50 4.92 4.43 4.92 2.73 n (Samp) 53 16 53 24 53 8 n (Patient) 52 16 52 24 52 8 UO only Median 0.830 0.839 0.830 0.771 0.830 0.604 Average 1.35 1.12 1.35 1.11 1.35 0.542 Stdev 1.17 0.997 1.17 1.06 1.17 0.148 p(t-test) 0.51 0.40 0.076 Min 0.0870 0.183 0.0870 0.191 0.0870 0.244 Max 4.92 3.50 4.92 4.43 4.92 0.684 n (Samp) 48 14 48 24 48 7 n (Patient) 44 14 44 24 44 7 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.55 nd 0.44 0.52 nd 0.45 0.40 nd 0.29 SE 0.084 nd 0.089 0.072 nd 0.073 0.11 nd 0.12 p 0.57 nd 0.53 0.80 nd 0.45 0.37 nd 0.063 nCohort 1 53 nd 48 53 nd 48 53 nd 48 nCohort 2 16 nd 14 24 nd 24 8 nd 7 Cutoff 1 0.658 nd 0.510 0.540 nd 0.540 0.540 nd 0.540 Sens 1 75% nd 71% 71% nd 71% 75% nd 71% Spec 1 45% nd 27% 36% nd 31% 36% nd 31% Cutoff 2 0.510 nd 0.308 0.340 nd 0.340 0.454 nd 0.454 Sens 2 81% nd 86% 83% nd 83% 88% nd 86% Spec 2 32% nd  6% 19% nd 12% 28% nd 25% Cutoff 3 0.183 nd 0.183 0.319 nd 0.308 0.236 nd 0.0870 Sens 3 94% nd 93% 92% nd 92% 100%  nd 100%  Spec 3  2% nd  2% 13% nd  6%  6% nd  2% Cutoff 4 1.22 nd 1.67 1.22 nd 1.67 1.22 nd 1.67 Sens 4 31% nd 21% 29% nd 21% 12% nd  0% Spec 4 72% nd 71% 72% nd 71% 72% nd 71% Cutoff 5 1.82 nd 2.14 1.82 nd 2.14 1.82 nd 2.14 Sens 5 25% nd 21% 25% nd 12% 12% nd  0% Spec 5 81% nd 81% 81% nd 81% 81% nd 81% Cutoff 6 3.14 nd 3.57 3.14 nd 3.57 3.14 nd 3.57 Sens 6  6% nd  0%  8% nd  4%  0% nd  0% Spec 6 91% nd 92% 91% nd 92% 91% nd 92% OR Quart 2 1.4 nd 1.6 1.3 nd 1.3 1.1 nd >0 p Value 0.67 nd 0.60 0.72 nd 0.72 0.96 nd <na   95% CI of 0.27 nd 0.29 0.32 nd 0.31 0.061 nd >na   OR Quart2 7.7 nd 8.6 5.3 nd 5.4 19 nd na OR Quart 3 1.4 nd 1.4 1.6 nd 2.1 7.5 nd >10 p Value 0.67 nd 0.67 0.49 nd 0.30 0.085 nd <0.044 95% CI of 0.27 nd 0.27 0.41 nd 0.52 0.76 nd >1.1 OR Quart3 7.7 nd 7.8 6.5 nd 8.3 74 nd na OR Quart 4 1.8 nd 1.1 1.2 nd 1.0 1.1 nd >1.2 p Value 0.48 nd 0.93 0.80 nd 1.0 0.96 nd <0.92 95% CI of 0.36 nd 0.18 0.30 nd 0.23 0.061 nd >0.066 OR Quart4 9.1 nd 6.4 4.9 nd 4.3 19 nd na Carbonic anhydrase IX 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.115 0.121 0.115 0.107 0.115 0.141 Average 0.155 0.126 0.155 0.209 0.155 0.146 Stdev 0.139 0.0833 0.139 0.374 0.139 0.0668 p(t-test) 0.44 0.35 0.86 Min 0.0145 0.00992 0.0145 0.0142 0.0145 0.0579 Max 0.796 0.310 0.796 1.90 0.796 0.246 n (Samp) 55 16 55 24 55 8 n (Patient) 54 16 54 24 54 8 UO only Median 0.124 0.156 0.124 0.117 0.124 0.135 Average 0.170 0.148 0.170 0.214 0.170 0.134 Stdev 0.158 0.0908 0.158 0.373 0.158 0.0629 p(t-test) 0.61 0.48 0.56 Min 0.0145 0.00992 0.0145 0.0142 0.0145 0.0579 Max 0.796 0.310 0.796 1.90 0.796 0.246 n (Samp) 49 14 49 24 49 7 n (Patient) 45 14 45 24 45 7 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.47 nd 0.51 0.48 nd 0.48 0.57 nd 0.51 SE 0.083 nd 0.089 0.071 nd 0.073 0.11 nd 0.12 p 0.72 nd 0.88 0.78 nd 0.76 0.56 nd 0.93 nCohort 1 55 nd 49 55 nd 49 55 nd 49 nCohort 2 16 nd 14 24 nd 24 8 nd 7 Cutoff 1 0.0795 nd 0.0877 0.0780 nd 0.0780 0.0919 nd 0.0901 Sens 1 75% nd 71% 71% nd 71% 75% nd 71% Spec 1 27% nd 33% 25% nd 24% 36% nd 35% Cutoff 2 0.0577 nd 0.0577 0.0665 nd 0.0635 0.0877 nd 0.0877 Sens 2 81% nd 86% 83% nd 83% 88% nd 86% Spec 2 18% nd 18% 24% nd 20% 33% nd 33% Cutoff 3 0.0156 nd 0.0156 0.0467 nd 0.0467 0.0577 nd 0.0577 Sens 3 94% nd 93% 92% nd 92% 100%  nd 100%  Spec 3  4% nd  4% 15% nd 12% 18% nd 18% Cutoff 4 0.166 nd 0.212 0.166 nd 0.212 0.166 nd 0.212 Sens 4 31% nd 21% 29% nd 29% 38% nd 14% Spec 4 71% nd 71% 71% nd 71% 71% nd 71% Cutoff 5 0.231 nd 0.238 0.231 nd 0.238 0.231 nd 0.238 Sens 5 12% nd 21% 29% nd 25% 12% nd 14% Spec 5 80% nd 82% 80% nd 82% 80% nd 82% Cutoff 6 0.325 nd 0.392 0.325 nd 0.392 0.325 nd 0.392 Sens 6  0% nd  0%  8% nd  8%  0% nd  0% Spec 6 91% nd 92% 91% nd 92% 91% nd 92% OR Quart 2 1.9 nd 0.92 0.62 nd 0.49 2.0 nd 2.2 p Value 0.43 nd 0.93 0.49 nd 0.33 0.59 nd 0.55 95% CI of 0.38 nd 0.16 0.16 nd 0.11 0.16 nd 0.17 OR Quart2 9.6 nd 5.5 2.4 nd 2.1 25 nd 27 OR Quart 3 1.4 nd 1.8 1.0 nd 1.1 3.2 nd 3.5 p Value 0.67 nd 0.48 1.0 nd 0.90 0.34 nd 0.30 95% CI of 0.27 nd 0.35 0.27 nd 0.29 0.30 nd 0.32 OR Quart3 7.5 nd 9.5 3.7 nd 4.1 35 nd 39 OR Quart 4 1.5 nd 0.92 0.66 nd 0.86 2.0 nd 1.0 p Value 0.61 nd 0.93 0.56 nd 0.82 0.59 nd 1.0 95% CI of 0.29 nd 0.16 0.17 nd 0.22 0.16 nd 0.056 OR Quart4 8.2 nd 5.5 2.6 nd 3.3 25 nd 18

TABLE 5 Comparison of marker levels in EDTA samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0 or R) and in EDTA samples collected from subjects at 0, 24 hours, and 48 hours prior to reaching stage I or F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 2.35 3.84 2.35 3.30 2.35 3.65 Average 2.95 4.81 2.95 4.65 2.95 4.18 Stdev 2.08 3.91 2.08 4.22 2.08 2.85 p(t-test) 4.1E−5 4.8E−5 0.019 Min 0.759 0.780 0.759 1.12 0.759 0.945 Max 16.5 16.7 16.5 22.7 16.5 11.3 n (Samp) 437 26 437 33 437 17 n (Patient) 174 26 174 33 174 17 sCr only Median 2.46 6.68 2.46 4.26 2.46 4.60 Average 3.12 5.93 3.12 7.26 3.12 5.82 Stdev 2.23 2.51 2.23 7.08 2.23 3.55 p(t-test) 0.0023 2.9E−7 0.0017 Min 0.729 2.87 0.729 1.84 0.729 1.90 Max 16.7 8.27 16.7 22.7 16.7 10.6 n (Samp) 535 6 535 9 535 7 n (Patient) 207 6 207 9 207 7 UO only Median 2.41 3.84 2.41 3.30 2.41 3.65 Average 3.03 4.81 3.03 4.24 3.03 4.32 Stdev 2.17 3.87 2.17 2.81 2.17 2.90 p(t-test) 1.7E−4 0.0039 0.019 Min 0.899 0.780 0.899 1.12 0.899 0.945 Max 16.5 16.7 16.5 11.9 16.5 11.3 n (Samp) 362 26 362 31 362 17 n (Patient) 140 26 140 31 140 17 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.69 0.83 0.69 0.65 0.72 0.65 0.65 0.75 0.66 SE 0.059 0.10 0.059 0.053 0.097 0.055 0.074 0.11 0.074 P 0.0014 0.0011 0.0017 0.0052 0.024 0.0056 0.048 0.018 0.033 nCohort 1 437 535 362 437 535 362 437 535 362 nCohort 2 26 6 26 33 9 31 17 7 17 Cutoff 1 2.60 2.93 2.60 2.10 2.27 2.52 2.33 4.35 2.45 Sens 1 73% 83% 73% 73% 78% 71% 71% 71% 71% Spec 1 56% 60% 55% 41% 44% 53% 50% 81% 52% Cutoff 2 2.38 2.93 2.38 1.88 1.88 1.96 1.88 2.19 2.27 Sens 2 81% 83% 81% 82% 89% 81% 82% 86% 82% Spec 2 50% 60% 49% 33% 31% 36% 33% 42% 45% Cutoff 3 1.47 2.86 1.47 1.56 1.83 1.56 1.43 1.88 1.43 Sens 3 92% 100%  92% 91% 100%  90% 94% 100%  94% Spec 3 18% 59% 18% 22% 30% 21% 16% 31% 17% Cutoff 4 3.17 3.47 3.31 3.17 3.47 3.31 3.17 3.47 3.31 Sens 4 58% 67% 62% 55% 67% 48% 59% 71% 59% Spec 4 70% 70% 70% 70% 70% 70% 70% 70% 70% Cutoff 5 3.83 4.30 3.95 3.83 4.30 3.95 3.83 4.30 3.95 Sens 5 50% 67% 42% 45% 44% 45% 41% 71% 35% Spec 5 80% 80% 80% 80% 80% 80% 80% 80% 80% Cutoff 6 5.37 5.58 5.50 5.37 5.58 5.50 5.37 5.58 5.50 Sens 6 23% 67% 19% 27% 33% 26% 24% 43% 24% Spec 6 90% 90% 90% 90% 90% 90% 90% 90% 90% OR Quart 2 0.99 >0 1.0 2.1 >3.1 1.3 0.99 >2.0 0.65 p Value 0.99 <na 1.0 0.25 <0.33 0.73 0.99 <0.57 0.64 95% CI of 0.20 >na 0.20 0.60 >0.32 0.33 0.20 >0.18 0.11 OR Quart2 5.0 na 5.1 7.0 na 4.9 5.0 na 4.0 OR Quart 3 2.0 >2.0 1.7 1.3 >0 2.1 0.33 >0 0.99 p Value 0.32 <0.57 0.47 0.73 <na 0.24 0.34 <na 0.99 95% CI of 0.50 >0.18 0.40 0.33 >na 0.61 0.034 >na 0.19 OR Quart3 8.3 na 7.3 4.8 na 7.2 3.2 na 5.0 OR Quart 4 5.1 >4.1 5.7 4.4 >6.3 3.9 3.5 >5.2 3.2 p Value 0.012 <0.21 0.0073 0.0097 <0.091 0.021 0.061 <0.14 0.091 95% CI of 1.4 >0.45 1.6 1.4 >0.75 1.2 0.94 >0.59 0.83 OR Quart4 18 na 21 14 na 12 13 na 12 Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median nd nd 3740 4690 nd nd Average nd nd 4070 6680 nd nd Stdev nd nd 1650 6470 nd nd p(t-test) nd nd 0.0015 nd nd Min nd nd 1120 2100 nd nd Max nd nd 10400 23300 nd nd n (Samp) nd nd 113 9 nd nd n (Patient) nd nd 92 9 nd nd UO only Median nd nd 3980 4690 nd nd Average nd nd 4160 6680 nd nd Stdev nd nd 1700 6470 nd nd p(t-test) nd nd 0.0035 nd nd Min nd nd 1120 2100 nd nd Max nd nd 10400 23300 nd nd n (Samp) nd nd 99 9 nd nd n (Patient) nd nd 77 9 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC nd nd nd 0.64 nd 0.62 nd nd nd SE nd nd nd 0.10 nd 0.10 nd nd nd p nd nd nd 0.17 nd 0.25 nd nd nd nCohort 1 nd nd nd 113 nd 99 nd nd nd nCohort 2 nd nd nd 9 nd 9 nd nd nd Cutoff 1 nd nd nd 3620 nd 3580 nd nd nd Sens 1 nd nd nd 78% nd 78% nd nd nd Spec 1 nd nd nd 47% nd 41% nd nd nd Cutoff 2 nd nd nd 3360 nd 3340 nd nd nd Sens 2 nd nd nd 89% nd 89% nd nd nd Spec 2 nd nd nd 41% nd 38% nd nd nd Cutoff 3 nd nd nd 2100 nd 2100 nd nd nd Sens 3 nd nd nd 100%  nd 100%  nd nd nd Spec 3 nd nd nd  5% nd  6% nd nd nd Cutoff 4 nd nd nd 4690 nd 4900 nd nd nd Sens 4 nd nd nd 56% nd 33% nd nd nd Spec 4 nd nd nd 71% nd 71% nd nd nd Cutoff 5 nd nd nd 5340 nd 5480 nd nd nd Sens 5 nd nd nd 33% nd 33% nd nd nd Spec 5 nd nd nd 81% nd 81% nd nd nd Cutoff 6 nd nd nd 6200 nd 6380 nd nd nd Sens 6 nd nd nd 33% nd 22% nd nd nd Spec 6 nd nd nd 90% nd 91% nd nd nd OR Quart 2 nd nd nd 2.0 nd 3.2 nd nd nd p Value nd nd nd 0.58 nd 0.32 nd nd nd 95% CI of nd nd nd 0.17 nd 0.32 nd nd nd OR Quart2 nd nd nd 23 nd 33 nd nd nd OR Quart 3 nd nd nd 3.2 nd 2.1 nd nd nd p Value nd nd nd 0.32 nd 0.56 nd nd nd 95% CI of nd nd nd 0.32 nd 0.18 nd nd nd OR Quart3 nd nd nd 33 nd 24 nd nd nd OR Quart 4 nd nd nd 3.1 nd 3.2 nd nd nd p Value nd nd nd 0.34 nd 0.32 nd nd nd 95% CI of nd nd nd 0.30 nd 0.32 nd nd nd OR Quart4 nd nd nd 32 nd 33 nd nd nd

TABLE 6 Comparison of the maximum marker levels in EDTA samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0) and the maximum values in EDTA samples collected from subjects between enrollment and 0, 24 hours, and 48 hours prior to reaching stage F in Cohort 2. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 2.63 7.26 2.63 6.24 2.63 5.57 Average 3.24 8.21 3.24 7.37 3.24 5.98 Stdev 2.18 5.22 2.18 5.28 2.18 3.16 p(t-test) 3.7E−10 1.1E−7 0.0012 Min 0.951 2.40 0.951 2.19 0.951 2.34 Max 12.1 22.7 12.1 22.7 12.1 11.3 n (Samp) 111 16 111 16 111 8 n (Patient) 111 16 111 16 111 8 sCr only Median 2.62 8.11 2.62 6.44 nd nd Average 3.34 9.20 3.34 8.54 nd nd Stdev 2.33 6.94 2.33 7.37 nd nd p(t-test) 5.7E−9 2.7E−7 nd nd Min 0.951 2.40 0.951 2.19 nd nd Max 16.7 22.7 16.7 22.7 nd nd n (Samp) 180 8 180 8 nd nd n (Patient) 180 8 180 8 nd nd UO only Median 2.66 7.62 2.66 6.90 2.66 5.57 Average 3.09 8.36 3.09 7.55 3.09 6.46 Stdev 1.97 3.54 1.97 3.23 1.97 3.33 p(t-test) 6.8E−11 7.4E−9 2.0E−4 Min 0.951 3.32 0.951 2.34 0.951 2.34 Max 12.1 14.6 12.1 11.9 12.1 11.3 n (Samp) 91 10 91 10 91 6 n (Patient) 91 10 91 10 91 6 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.86 0.82 0.93 0.80 0.74 0.89 0.79 nd 0.83 SE 0.060 0.092 0.058 0.069 0.10 0.069 0.098 nd 0.11 p 1.6E−9 4.2E−4 1.5E−13 1.5E−5 0.018 2.2E−8 0.0035 nd 0.0018 nCohort 1 111 180 91 111 180 91 111 nd 91 nCohort 2 16 8 10 16 8 10 8 nd 6 Cutoff 1 4.35 3.32 6.82 4.16 2.38 5.62 4.35 nd 4.35 Sens 1 75% 75% 70% 75% 75% 70% 75% nd 83% Spec 1 77% 66% 97% 76% 44% 88% 77% nd 81% Cutoff 2 3.32 2.93 5.62 2.38 2.27 5.39 2.38 nd 4.35 Sens 2 81% 88% 80% 81% 88% 80% 88% nd 83% Spec 2 67% 57% 88% 46% 41% 87% 46% nd 81% Cutoff 3 2.93 2.38 4.35 2.26 2.17 4.35 2.30 nd 2.30 Sens 3 94% 100%  90% 94% 100%  90% 100%  nd 100%  Spec 3 59% 44% 81% 42% 37% 81% 44% nd 43% Cutoff 4 3.61 3.62 3.43 3.61 3.62 3.43 3.61 nd 3.43 Sens 4 75% 62% 90% 75% 62% 90% 75% nd 83% Spec 4 70% 70% 70% 70% 70% 70% 70% nd 70% Cutoff 5 4.76 4.76 4.31 4.76 4.76 4.31 4.76 nd 4.31 Sens 5 69% 62% 90% 62% 50% 90% 62% nd 83% Spec 5 81% 80% 80% 81% 80% 80% 81% nd 80% Cutoff 6 6.14 6.17 6.04 6.14 6.17 6.04 6.14 nd 6.04 Sens 6 62% 62% 70% 50% 50% 60% 38% nd 33% Spec 6 90% 90% 90% 90% 90% 90% 90% nd 90% OR Quart 2 >1.0 >1.0 >0 >4.4 >3.2 >1.0 >2.1 nd >1.0 p Value <1.0 <0.99 <na <0.19 <0.32 <0.98 <0.56 nd <0.98 95% CI of >0.060 >0.062 >na >0.47 >0.32 >0.062 >0.18 nd >0.062 OR Quart2 na na na na na na na nd na OR Quart 3 >4.4 >2.1 >1.0 >2.1 >1.0 >0 >1.0 nd >0 p Value <0.19 <0.55 <0.98 <0.56 <0.99 <na <1.0 nd <na 95% CI of >0.47 >0.18 >0.062 >0.18 >0.062 >na >0.060 nd >na OR Quart3 na na na na na na na nd na OR Quart 4 >16 >5.6 >13 >14 >4.4 >13 >5.8 nd >6.0 p Value <0.0100 <0.12 <0.019 <0.015 <0.19 <0.019 <0.12 nd <0.11 95% CI of >1.9 >0.63 >1.5 >1.7 >0.47 >1.5 >0.63 nd >0.65 OR Quart4 na na na na na na na nd na

TABLE 7 Comparison of marker levels in urine samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0, R, or I) and in urine samples collected from Cohort 2 (subjects who progress to RIFLE stage F) at 0, 24 hours, and 48 hours prior to the subject reaching RIFLE stage I. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 1.51 0.990 1.51 0.202 nd nd Average 2.57 2.02 2.57 1.80 nd nd Stdev 2.44 2.22 2.44 2.59 nd nd p(t-test) 0.48 0.30 nd nd Min 0.00152 0.00133 0.00152 0.00212 nd nd Max 6.10 5.64 6.10 5.80 nd nd n (Samp) 534 10 534 11 nd nd n (Patient) 204 10 204 11 nd nd UO only Median 1.60 0.480 1.60 0.163 nd nd Average 2.61 1.86 2.61 0.998 nd nd Stdev 2.44 2.11 2.44 1.98 nd nd p(t-test) 0.42 0.064 nd nd Min 0.00152 0.00403 0.00152 0.00212 nd nd Max 6.10 4.76 6.10 5.80 nd nd n (Samp) 454 7 454 8 nd nd n (Patient) 168 7 168 8 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.40 nd 0.38 0.40 nd 0.29 nd nd nd SE 0.096 nd 0.11 0.091 nd 0.10 nd nd nd p 0.29 nd 0.31 0.25 nd 0.044 nd nd nd nCohort 1 534 nd 454 534 nd 454 nd nd nd nCohort 2 10 nd 7 11 nd 8 nd nd nd Cutoff 1 0.260 nd 0.214 0.153 nd 0.0999 nd nd nd Sens 1 70% nd 71% 73% nd 75% nd nd nd Spec 1 28% nd 25% 22% nd 17% nd nd nd Cutoff 2 0.0899 nd 0.0899 0.100 nd 0.0301 nd nd nd Sens 2 80% nd 86% 82% nd 88% nd nd nd Spec 2 17% nd 16% 18% nd  7% nd nd nd Cutoff 3 0.00347 nd 0.00347 0.0319 nd 0.00181 nd nd nd Sens 3 90% nd 100%  91% nd 100%  nd nd nd Spec 3  1% nd  1%  7% nd  0% nd nd nd Cutoff 4 5.13 nd 5.20 5.13 nd 5.20 nd nd nd Sens 4 10% nd  0% 27% nd 12% nd nd nd Spec 4 70% nd 70% 70% nd 70% nd nd nd Cutoff 5 5.80 nd 5.80 5.80 nd 5.80 nd nd nd Sens 5  0% nd  0%  0% nd  0% nd nd nd Spec 5 95% nd 94% 95% nd 94% nd nd nd Cutoff 6 5.80 nd 5.80 5.80 nd 5.80 nd nd nd Sens 6  0% nd  0%  0% nd  0% nd nd nd Spec 6 95% nd 94% 95% nd 94% nd nd nd OR Quart 2 >5.2 nd >3.1 0 nd 0 nd nd nd p Value <0.14 nd <0.33 na nd na nd nd nd 95% CI of >0.60 nd >0.32 na nd na nd nd nd OR Quart2 na nd na na nd na nd nd nd OR Quart 3 >2.0 nd >1.0 1.0 nd 2.0 nd nd nd p Value <0.57 nd <0.99 0.99 nd 0.57 nd nd nd 95% CI of >0.18 nd >0.063 0.20 nd 0.18 nd nd nd OR Quart3 na nd na 5.1 nd 23 nd nd nd OR Quart 4 >3.1 nd >3.1 1.7 nd 5.2 nd nd nd p Value <0.33 nd <0.33 0.47 nd 0.13 nd nd nd 95% CI of >0.32 nd >0.32 0.40 nd 0.60 nd nd nd OR Quart4 na nd na 7.3 nd 45 nd nd nd C-X-C motif chemokine 2 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.689 11.6 0.689 27.9 0.689 3.59 Average 8.05 33.9 8.05 45.6 8.05 7.16 Stdev 22.2 60.3 22.2 62.5 22.2 8.31 p(t-test) 6.7E−5 3.2E−10 0.92 Min 0.00804 0.0260 0.00804 0.534 0.00804 0.0260 Max 266 217 266 217 266 18.5 n (Samp) 932 13 932 16 932 7 n (Patient) 343 13 343 16 343 7 sCr only Median 0.895 27.8 nd nd nd nd Average 8.75 52.6 nd nd nd nd Stdev 23.4 76.5 nd nd nd nd p(t-test) 2.0E−6 nd nd nd nd Min 0.00804 0.0260 nd nd nd nd Max 266 217 nd nd nd nd n (Samp) 969 7 nd nd nd nd n (Patient) 353 7 nd nd nd nd UO only Median 0.805 9.01 0.805 28.6 nd nd Average 8.30 46.4 8.30 49.6 nd nd Stdev 22.4 75.1 22.4 66.0 nd nd p(t-test) 4.9E−6 1.8E−10 nd nd Min 0.00804 0.0260 0.00804 0.534 nd nd Max 266 217 266 217 nd nd n (Samp) 797 8 797 14 nd nd n (Patient) 260 8 260 14 nd nd 0 hr prior to AKI stage 24hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.63 0.73 0.62 0.83 nd 0.82 0.59 nd nd SE 0.084 0.11 0.11 0.064 nd 0.069 0.11 nd nd p 0.13 0.039 0.25 2.1E−7 nd 2.6E−6 0.44 nd nd nCohort 1 932 969 797 932 nd 797 932 nd nd nCohort 2 13 7 8 16 nd 14 7 nd nd Cutoff 1 0.00804 11.6 0.00804 6.36 nd 11.6 0.135 nd nd Sens 1 100%  71% 100%  75% nd 71% 71% nd nd Spec 1  0% 82%  0% 75% nd 83% 43% nd nd Cutoff 2 0.00804 0.00804 0.00804 1.64 nd 1.54 0.00804 nd nd Sens 2 100%  100%  100%  81% nd 86% 100%  nd nd Spec 2  0%  0%  0% 56% nd 54%  0% nd nd Cutoff 3 0.00804 0.00804 0.00804 1.45 nd 1.45 0.00804 nd nd Sens 3 100%  100%  100%  94% nd 93% 100%  nd nd Spec 3  0%  0%  0% 54% nd 53%  0% nd nd Cutoff 4 4.46 5.17 4.82 4.46 nd 4.82 4.46 nd nd Sens 4 54% 71% 50% 75% nd 71% 43% nd nd Spec 4 70% 70% 70% 70% nd 70% 70% nd nd Cutoff 5 8.41 9.64 8.68 8.41 nd 8.68 8.41 nd nd Sens 5 54% 71% 50% 69% nd 71% 43% nd nd Spec 5 80% 80% 80% 80% nd 80% 80% nd nd Cutoff 6 19.3 20.9 20.1 19.3 nd 20.1 19.3 nd nd Sens 6 38% 57% 38% 62% nd 64%  0% nd nd Spec 6 90% 90% 90% 90% nd 90% 90% nd nd OR Quart 2 0 >2.0 >3.0 >1.0 nd >1.0 0.50 nd nd p Value na <0.57 <0.34 <1.00 nd <1.0 0.57 nd nd 95% CI of na >0.18 >0.31 >0.062 nd >0.062 0.045 nd nd OR Quart2 na na na na nd na 5.5 nd nd OR Quart 3 0.20 >0 >1.0 >4.1 nd >3.0 0.50 nd nd p Value 0.14 <na <1.00 <0.21 nd <0.34 0.57 nd nd 95% CI of 0.023 >na >0.062 >0.45 nd >0.31 0.045 nd nd OR Quart3 1.7 na na na nd na 5.5 nd nd OR Quart 4 1.4 >5.1 >4.1 >12 nd >10 1.5 nd nd p Value 0.57 <0.14 <0.21 <0.020 nd <0.026 0.66 nd nd 95% CI of 0.44 >0.59 >0.45 >1.5 nd >1.3 0.25 nd nd OR Quart4 4.5 na na na nd na 9.1 nd nd Renin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 384 670 384 3140 nd nd Average 850 1270 850 4360 nd nd Stdev 1270 1520 1270 6140 nd nd p(t-test) 0.39 6.2E−11 nd nd Min 1.00E−9 78.9 1.00E−9 226 nd nd Max 9810 4050 9810 21100 nd nd n (Samp) 322 7 322 10 nd nd n (Patient) 188 7 188 10 nd nd UO only Median nd nd 396 3330 nd nd Average nd nd 905 4940 nd nd Stdev nd nd 1320 6790 nd nd p(t-test) nd nd 1.3E−10 nd nd Min nd nd 1.00E−9 226 nd nd Max nd nd 9810 21100 nd nd n (Samp) nd nd 280 8 nd nd n (Patient) nd nd 157 8 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.60 nd nd 0.82 nd 0.81 nd nd nd SE 0.11 nd nd 0.083 nd 0.093 nd nd nd p 0.38 nd nd 1.3E−4 nd 8.4E−4 nd nd nd nCohort 1 322 nd nd 322 nd 280 nd nd nd nCohort 2 7 nd nd 10 nd 8 nd nd nd Cutoff 1 310 nd nd 1480 nd 1480 nd nd nd Sens 1 71% nd nd 70% nd 75% nd nd nd Spec 1 46% nd nd 81% nd 80% nd nd nd Cutoff 2 97.3 nd nd 667 nd 407 nd nd nd Sens 2 86% nd nd 80% nd 88% nd nd nd Spec 2 24% nd nd 66% nd 51% nd nd nd Cutoff 3 69.5 nd nd 407 nd 225 nd nd nd Sens 3 100%  nd nd 90% nd 100%  nd nd nd Spec 3 22% nd nd 53% nd 34% nd nd nd Cutoff 4 804 nd nd 804 nd 865 nd nd nd Sens 4 43% nd nd 70% nd 75% nd nd nd Spec 4 70% nd nd 70% nd 70% nd nd nd Cutoff 5 1440 nd nd 1440 nd 1520 nd nd nd Sens 5 29% nd nd 70% nd 62% nd nd nd Spec 5 80% nd nd 80% nd 80% nd nd nd Cutoff 6 2280 nd nd 2280 nd 2350 nd nd nd Sens 6 29% nd nd 60% nd 62% nd nd nd Spec 6 90% nd nd 90% nd 90% nd nd nd OR Quart 2 0.49 nd nd >1.0 nd >2.1 nd nd nd p Value 0.57 nd nd <0.99 nd <0.56 nd nd nd 95% CI of 0.044 nd nd >0.062 nd >0.18 nd nd nd OR Quart2 5.6 nd nd na nd na nd nd nd OR Quart 3 1.0 nd nd >2.0 nd >0 nd nd nd p Value 1.0 nd nd <0.56 nd <na nd nd nd 95% CI of 0.14 nd nd >0.18 nd >na nd nd nd OR Quart3 7.3 nd nd na nd na nd nd nd OR Quart 4 0.99 nd nd >7.6 nd >6.5 nd nd nd p Value 0.99 nd nd <0.060 nd <0.086 nd nd nd 95% CI of 0.14 nd nd >0.92 nd >0.77 nd nd nd OR Quart4 7.2 nd nd na nd na nd nd nd Cathepsin B 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 0.632 1.86 0.632 2.76 nd nd Average 2.59 3.31 2.59 13.5 nd nd Stdev 8.00 4.58 8.00 20.9 nd nd p(t-test) 0.81  9.4E−5 nd nd Min 1.00E−9 1.00E−9 1.00E−9 1.00E−9 nd nd Max 78.1 12.7 78.1 64.9 nd nd n (Samp) 339 7 339 10 nd nd n (Patient) 194 7 194 10 nd nd UO only Median nd nd 0.726 2.35 nd nd Average nd nd 2.90 13.5 nd nd Stdev nd nd 8.59 23.0 nd nd p(t-test) nd nd 0.0014 nd nd Min nd nd 1.00E−9 1.00E−9 nd nd Max nd nd 78.1 64.9 nd nd n (Samp) nd nd 295 8 nd nd n (Patient) nd nd 162 8 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.58 nd nd 0.75 nd 0.70 nd nd nd SE 0.11 nd nd 0.091 nd 0.11 nd nd nd p 0.51 nd nd 0.0065 nd 0.059 nd nd nd nCohort 1 339 nd nd 339 nd 295 nd nd nd nCohort 2 7 nd nd 10 nd 8 nd nd nd Cutoff 1 0.397 nd nd 1.39 nd 0.973 nd nd nd Sens 1 71% nd nd 70% nd 75% nd nd nd Spec 1 38% nd nd 70% nd 58% nd nd nd Cutoff 2 0.0840 nd nd 0.973 nd 0.924 nd nd nd Sens 2 86% nd nd 80% nd 88% nd nd nd Spec 2 15% nd nd 60% nd 57% nd nd nd Cutoff 3 0 nd nd 0.924 nd 0 nd nd nd Sens 3 100%  nd nd 90% nd 100%  nd nd nd Spec 3  0% nd nd 59% nd  0% nd nd nd Cutoff 4 1.41 nd nd 1.41 nd 1.57 nd nd nd Sens 4 57% nd nd 60% nd 50% nd nd nd Spec 4 70% nd nd 70% nd 70% nd nd nd Cutoff 5 2.48 nd nd 2.48 nd 2.74 nd nd nd Sens 5 43% nd nd 50% nd 50% nd nd nd Spec 5 80% nd nd 80% nd 80% nd nd nd Cutoff 6 5.07 nd nd 5.07 nd 5.47 nd nd nd Sens 6 29% nd nd 40% nd 38% nd nd nd Spec 6 90% nd nd 90% nd 90% nd nd nd OR Quart 2 0.49 nd nd 0 nd 0 nd nd nd p Value 0.56 nd nd na nd na nd nd nd 95% CI of 0.043 nd nd na nd na nd nd nd OR Quart2 5.5 nd nd na nd na nd nd nd OR Quart 3 0.49 nd nd 3.1 nd 3.0 nd nd nd p Value 0.57 nd nd 0.34 nd 0.34 nd nd nd 95% CI of 0.044 nd nd 0.31 nd 0.31 nd nd nd OR Quart3 5.6 nd nd 30 nd 30 nd nd nd OR Quart 4 1.5 nd nd 6.3 nd 4.1 nd nd nd p Value 0.66 nd nd 0.092 nd 0.21 nd nd nd 95% CI of 0.24 nd nd 0.74 nd 0.45 nd nd nd OR Quart4 9.2 nd nd 53 nd 38 nd nd nd Dipeptidyl peptidase IV 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 197 1310 197 1010 nd nd Average 3440 2090 3440 2020 nd nd Stdev 42400 2430 42400 2600 nd nd p(t-test) 0.94 0.92 nd nd Min 0.200 0.651 0.200 10.1 nd nd Max 677000 5420 677000 7150 nd nd n (Samp) 255 6 255 8 nd nd n (Patient) 158 6 158 8 nd nd UO only Median nd nd 197 847 nd nd Average nd nd 706 1390 nd nd Stdev nd nd 1510 1830 nd nd p(t-test) nd nd 0.28 nd nd Min nd nd 0.200 10.1 nd nd Max nd nd 12500 4950 nd nd n (Samp) nd nd 221 6 nd nd n (Patient) nd nd 134 6 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.59 nd nd 0.71 nd 0.67 nd nd nd SE 0.12 nd nd 0.10 nd 0.12 nd nd nd p 0.49 nd nd 0.049 nd 0.18 nd nd nd nCohort 1 255 nd nd 255 nd 221 nd nd nd nCohort 2 6 nd nd 8 nd 6 nd nd nd Cutoff 1 52.3 nd nd 337 nd 294 nd nd nd Sens 1 83% nd nd 75% nd 83% nd nd nd Spec 1 29% nd nd 58% nd 57% nd nd nd Cutoff 2 52.3 nd nd 294 nd 294 nd nd nd Sens 2 83% nd nd 88% nd 83% nd nd nd Spec 2 29% nd nd 56% nd 57% nd nd nd Cutoff 3 0.202 nd nd 9.55 nd 9.55 nd nd nd Sens 3 100%  nd nd 100%  nd 100%  nd nd nd Spec 3  1% nd nd 11% nd 12% nd nd nd Cutoff 4 623 nd nd 623 nd 623 nd nd nd Sens 4 50% nd nd 62% nd 50% nd nd nd Spec 4 70% nd nd 70% nd 70% nd nd nd Cutoff 5 1020 nd nd 1020 nd 942 nd nd nd Sens 5 50% nd nd 50% nd 50% nd nd nd Spec 5 80% nd nd 80% nd 80% nd nd nd Cutoff 6 1810 nd nd 1810 nd 1580 nd nd nd Sens 6 50% nd nd 25% nd 17% nd nd nd Spec 6 90% nd nd 90% nd 90% nd nd nd OR Quart 2 2.0 nd nd 0 nd 0 nd nd nd p Value 0.57 nd nd na nd na nd nd nd 95% CI of 0.18 nd nd na nd na nd nd nd OR Quart2 23 nd nd na nd na nd nd nd OR Quart 3 0 nd nd 3.0 nd 2.0 nd nd nd p Value na nd nd 0.34 nd 0.58 nd nd nd 95% CI of na nd nd 0.31 nd 0.18 nd nd nd OR Quart3 na nd nd 30 nd 23 nd nd nd OR Quart 4 3.0 nd nd 4.1 nd 3.1 nd nd nd p Value 0.34 nd nd 0.21 nd 0.34 nd nd nd 95% CI of 0.31 nd nd 0.45 nd 0.31 nd nd nd OR Quart4 30 nd nd 38 nd 30 nd nd nd

TABLE 8 Comparison of marker levels in EDTA samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0, R, or I) and in EDTA samples collected from Cohort 2 (subjects who progress to RIFLE stage F) at 0, 24 hours, and 48 hours prior to the subject reaching RIFLE stage I. Beta-2-microglobulin 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 sCr or UO Median 2.46 5.00 2.46 5.64 nd nd Average 3.12 6.46 3.12 7.49 nd nd Stdev 2.19 3.84 2.19 6.07 nd nd p(t-test) 3.9E−7 1.0E−9 nd nd Min 0.729 2.19 0.729 1.52 nd nd Max 16.7 14.6 16.7 22.7 nd nd n (Samp) 551 12 551 11 nd nd n (Patient) 213 12 213 11 nd nd UO only Median 2.54 6.19 2.54 5.64 nd nd Average 3.15 7.19 3.15 6.53 nd nd Stdev 2.22 3.93 2.22 3.65 nd nd p(t-test) 7.7E−7 1.1E−5 nd nd Min 0.729 3.32 0.729 1.52 nd nd Max 16.7 14.6 16.7 11.9 nd nd n (Samp) 464 8 464 9 nd nd n (Patient) 173 8 173 9 nd nd 0 hr prior to AKI stage 24 hr prior to AKI stage 48 hr prior to AKI stage sCr or UO sCr only UO only sCr or UO sCr only UO only sCr or UO sCr only UO only AUC 0.82 nd 0.88 0.78 nd 0.79 nd nd nd SE 0.075 nd 0.079 0.083 nd 0.090 nd nd nd p 1.7E−5 nd 1.8E−6 6.7E−4 nd 0.0011 nd nd nd nCohort 1 551 nd 464 551 nd 464 nd nd nd nCohort 2 12 nd 8 11 nd 9 nd nd nd Cutoff 1 3.81 nd 4.59 4.43 nd 4.43 nd nd nd Sens 1 75% nd 75% 73% nd 78% nd nd nd Spec 1 75% nd 83% 82% nd 82% nd nd nd Cutoff 2 3.31 nd 3.81 2.31 nd 2.31 nd nd nd Sens 2 83% nd 88% 82% nd 89% nd nd nd Spec 2 68% nd 74% 46% nd 44% nd nd nd Cutoff 3 2.93 nd 3.31 2.27 nd 1.51 nd nd nd Sens 3 92% nd 100%  91% nd 100%  nd nd nd Spec 3 60% nd 67% 44% nd 18% nd nd nd Cutoff 4 3.48 nd 3.58 3.48 nd 3.58 nd nd nd Sens 4 75% nd 88% 73% nd 78% nd nd nd Spec 4 70% nd 70% 70% nd 70% nd nd nd Cutoff 5 4.31 nd 4.35 4.31 nd 4.35 nd nd nd Sens 5 58% nd 75% 73% nd 78% nd nd nd Spec 5 80% nd 80% 80% nd 80% nd nd nd Cutoff 6 5.57 nd 5.57 5.57 nd 5.57 nd nd nd Sens 6 42% nd 50% 55% nd 56% nd nd nd Spec 6 90% nd 90% 90% nd 90% nd nd nd OR Quart 2 >1.0 nd >0 2.0 nd 1.0 nd nd nd p Value <1.0 nd <na  0.57 nd 1.0 nd nd nd 95% CI of >0.062 nd >na  0.18 nd 0.062 nd nd nd OR Quart2 na nd na 22 nd 16 nd nd nd OR Quart 3 >3.0 nd >2.0 0 nd 0 nd nd nd p Value <0.34 nd <0.56 na nd na nd nd nd 95% CI of >0.31 nd >0.18 na nd na nd nd nd OR Quart3 na nd na na nd na nd nd nd OR Quart 4 >8.4 nd >6.3 8.4 nd 7.3 nd nd nd p Value <0.046 nd <0.090 0.047 nd 0.065 nd nd nd 95% CI of >1.0 nd >0.75 1.0 nd 0.89 nd nd nd OR Quart4 na nd na 68 nd 60 nd nd nd

TABLE 9 Comparison of marker levels in enroll urine samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0 or R within 48 hrs) and in enroll urine samples collected from Cohort 2 (subjects reaching RIFLE stage I or F within 48 hrs). Enroll samples from patients already at RIFLE stage I or F were included in Cohort 2. Beta-2-microglobulin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 1.58 0.320 1.10 0.745 1.48 0.289 Average 2.51 1.59 2.33 2.38 2.49 1.43 Stdev 2.46 2.27 2.44 2.80 2.47 2.15 p(t-test) 0.046 0.95 0.034 Min 0.00152 0.00133 0.00152 0.00133 0.00152 0.00212 Max 6.10 6.07 6.10 5.80 6.10 6.07 n (Samp) 138 35 164 8 111 30 n (Patient) 138 35 164 8 111 30 At Enrollment sCr or UO sCr only UO only AUC 0.37 0.49 0.35 SE 0.055 0.11 0.060 p 0.017 0.93 0.014 nCohort 1 138 164 111 nCohort 2 35 8 30 Cutoff 1 0.0372 0.255 0.0372 Sens 1 71% 75% 70% Spec 1 10% 35% 11% Cutoff 2 0.0182 0.0627 0.0182 Sens 2 80% 88% 80% Spec 2  5% 19%  5% Cutoff 3 0.00270 0 0.00408 Sens 3 91% 100%  90% Spec 3  1%  0%  3% Cutoff 4 5.08 4.82 5.08 Sens 4 20% 38% 17% Spec 4 70% 70% 70% Cutoff 5 5.80 5.80 5.80 Sens 5  3%  0%  3% Spec 5 95% 95% 95% Cutoff 6 5.80 5.80 5.80 Sens 6  3%  0%  3% Spec 6 95% 95% 95% OR Quart 2 0.70 0 1.3 p Value 0.56 na 0.71 95% CI of 0.20 na 0.35 OR Quart2 2.4 na 4.7 OR Quart 3 1.6 1.0 1.8 p Value 0.39 1.0 0.33 95% CI of 0.55 0.19 0.54 OR Quart3 4.7 5.3 6.3 OR Quart 4 2.3 0.65 2.8 p Value 0.12 0.65 0.084 95% CI of 0.81 0.10 0.87 OR Quart4 6.5 4.1 9.3 C-X-C motif chemokine 2 sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 0.129 5.17 0.279 17.3 0.137 4.46 Average 8.07 22.1 9.66 35.0 8.19 23.9 Stdev 26.5 45.2 29.3 59.8 26.5 47.2 p(t-test) 0.0012 0.0052 0.0013 Min 0.00804 0.0260 0.00804 0.0260 0.00804 0.0260 Max 266 217 266 217 266 217 n (Samp) 292 61 338 12 211 55 n (Patient) 292 61 338 12 211 55 At Enrollment sCr or UO sCr only UO only AUC 0.66 0.77 0.66 SE 0.041 0.081 0.044 p 7.9E−5 9.7E−4 1.8E−4 nCohort 1 292 338 211 nCohort 2 61 12 55 Cutoff 1 0.297 6.27 0.297 Sens 1 70% 75% 71% Spec 1 54% 75% 54% Cutoff 2 0.00804 5.62 0.00804 Sens 2 100%  83% 100%  Spec 2  0% 72%  0% Cutoff 3 0.00804 0.00804 0.00804 Sens 3 100%  100%  100%  Spec 3  0%  0%  0% Cutoff 4 3.89 4.33 3.95 Sens 4 52% 83% 51% Spec 4 70% 70% 70% Cutoff 5 6.98 8.37 7.79 Sens 5 43% 67% 44% Spec 5 80% 80% 80% Cutoff 6 16.4 20.5 14.8 Sens 6 30% 50% 36% Spec 6 90% 90% 90% OR Quart 2 0.16 0 0.17 p Value 0.0046 na 0.0084 95% CI of 0.044 na 0.047 OR Quart 2 0.57 na 0.64 OR Quart 3 0.85 1.0 1.0 p Value 0.69 1.0 1.0 95% CI of 0.39 0.14 0.43 OR Quart 3 1.9 7.3 2.3 OR Quart 4 2.1 4.2 2.1 p Value 0.043 0.073 0.065 95% CI of 1.0 0.88 0.96 OR Quart 4 4.2 21 4.5 Renin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 346 1010 nd nd 344 1250 Average 771 2410 nd nd 800 2590 Stdev 1050 4300 nd nd 1090 4450 p(t-test) 5.2E−4 nd nd 7.8E−4 Min 1.00E−9 92.1 nd nd 1.00E−9 92.1 Max 4830 21100 nd nd 4830 21100 n (Samp) 109 24 nd nd 90 22 n (Patient) 109 24 nd nd 90 22 At Enrollment sCr or UO sCr only UO only AUC 0.70 nd 0.72 SE 0.064 nd 0.066 p 0.0018 nd 0.0012 nCohort 1 109 nd 90 nCohort 2 24 nd 22 Cutoff 1 394 nd 394 Sens 1 71% nd 73% Spec 1 52% nd 52% Cutoff 2 310 nd 346 Sens 2 83% nd 82% Spec 2 48% nd 51% Cutoff 3 97.3 nd 114 Sens 3 92% nd 91% Spec 3 27% nd 28% Cutoff 4 730 nd 730 Sens 4 58% nd 64% Spec 4 71% nd 70% Cutoff 5 1440 nd 1440 Sens 5 42% nd 45% Spec 5 81% nd 80% Cutoff 6 2150 nd 2150 Sens 6 38% nd 41% Spec 6 91% nd 90% OR Quart 2 1.8 nd 1.8 p Value 0.46 nd 0.45 95% CI of 0.39 nd 0.39 OR Quart2 8.2 nd 8.4 OR Quart 3 2.2 nd 1.4 p Value 0.29 nd 0.69 95% CI of 0.51 nd 0.28 OR Quart3 9.8 nd 6.9 OR Quart 4 4.2 nd 4.6 p Value 0.045 nd 0.035 95% CI of 1.0 nd 1.1 OR Quart4 17 nd 19 Cathepsin B sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 0.640 1.39 nd nd 0.760 1.39 Average 2.41 7.35 nd nd 2.72 6.90 Stdev 5.89 14.4 nd nd 6.66 14.6 p(t-test) 0.0073 nd nd 0.046 Min 1.00E−9 1.00E−9 nd nd 1.00E−9 1.00E−9 Max 51.8 64.9 nd nd 51.8 64.9 n (Samp) 110 24 nd nd 91 22 n (Patient) 110 24 nd nd 91 22 At Enrollment sCr or UO sCr only UO only AUC 0.64 nd 0.63 SE 0.066 nd 0.069 p 0.029 nd 0.061 nCohort 1 110 nd 91 nCohort 2 24 nd 22 Cutoff 1 0.604 nd 0.604 Sens 1 71% nd 73% Spec 1 50% nd 47% Cutoff 2 0.388 nd 0.460 Sens 2 83% nd 82% Spec 2 37% nd 37% Cutoff 3 0.148 nd 0.148 Sens 3 92% nd 91% Spec 3 18% nd 18% Cutoff 4 1.29 nd 1.29 Sens 4 54% nd 55% Spec 4 70% nd 70% Cutoff 5 2.34 nd 2.34 Sens 5 42% nd 41% Spec 5 80% nd 80% Cutoff 6 5.45 nd 7.18 Sens 6 25% nd 23% Spec 6 90% nd 90% OR Quart 2 1.2 nd 1.0 p Value 0.76 nd 1.0 95% CI of 0.30 nd 0.22 OR Quart2 5.1 nd 4.5 OR Quart 3 1.3 nd 1.3 p Value 0.72 nd 0.72 95% CI of 0.31 nd 0.31 OR Quart3 5.3 nd 5.5 OR Quart 4 3.0 nd 2.7 p Value 0.090 nd 0.14 95% CI of 0.84 nd 0.72 OR Quart4 11 nd 10 Neprilysin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 1.28 1.52 nd nd 1.28 1.32 Average 6.20 17.1 nd nd 5.94 19.1 Stdev 16.9 25.3 nd nd 17.0 26.3 p(t-test) 0.11 nd nd 0.074 Min 0.0869 0.0203 nd nd 0.0869 0.0203 Max 98.9 64.3 nd nd 98.9 64.3 n (Samp) 50 9 nd nd 42 8 n (Patient) 50 9 nd nd 42 8 At Enrollment sCr or UO sCr only UO only AUC 0.57 nd 0.57 SE 0.11 nd 0.11 p 0.51 nd 0.53 nCohort 1 50 nd 42 nCohort 2 9 nd 8 Cutoff 1 0.820 nd 0.820 Sens 1 78% nd 75% Spec 1 40% nd 43% Cutoff 2 0.238 nd 0.238 Sens 2 89% nd 88% Spec 2 10% nd 10% Cutoff 3 0 nd 0 Sens 3 100%  nd 100%  Spec 3  0% nd  0% Cutoff 4 1.68 nd 1.68 Sens 4 33% nd 38% Spec 4 70% nd 71% Cutoff 5 3.30 nd 3.50 Sens 5 33% nd 38% Spec 5 80% nd 81% Cutoff 6 10.8 nd 10.8 Sens 6 33% nd 38% Spec 6 90% nd 90% OR Quart 2 0.92 nd 0.91 p Value 0.94 nd 0.93 95% CI of 0.11 nd 0.11 OR Quart2 7.6 nd 7.7 OR Quart 3 0.92 nd 0.45 p Value 0.94 nd 0.54 95% CI of 0.11 nd 0.036 OR Quart3 7.6 nd 5.8 OR Quart 4 1.5 nd 1.5 p Value 0.69 nd 0.69 95% CI of 0.21 nd 0.20 OR Quart4 11 nd 11 Carbonic anhydrase IX sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 0.0111 0.0219 nd nd 0.0113 0.0232 Average 0.0193 0.114 nd nd 0.0192 0.126 Stdev 0.0252 0.280 nd nd 0.0259 0.297 p(t-test) 0.018 nd nd 0.021 Min 0.000386 0.00345 nd nd 0.00102 0.00345 Max 0.119 0.859 nd nd 0.119 0.859 n (Samp) 50 9 nd nd 42 8 n (Patient) 50 9 nd nd 42 8 At Enrollment sCr or UO sCr only UO only AUC 0.70 nd 0.71 SE 0.10 nd 0.11 p 0.054 nd 0.058 nCohort 1 50 nd 42 nCohort 2 9 nd 8 Cutoff 1 0.0179 nd 0.0179 Sens 1 78% nd 75% Spec 1 68% nd 69% Cutoff 2 0.0121 nd 0.0121 Sens 2 89% nd 88% Spec 2 58% nd 57% Cutoff 3 0.00296 nd 0.00296 Sens 3 100%  nd 100%  Spec 3 26% nd 24% Cutoff 4 0.0205 nd 0.0205 Sens 4 56% nd 50% Spec 4 70% nd 71% Cutoff 5 0.0284 nd 0.0274 Sens 5 22% nd 38% Spec 5 80% nd 81% Cutoff 6 0.0421 nd 0.0358 Sens 6 11% nd 12% Spec 6 90% nd 90% OR Quart 2 0 nd 0 p Value na nd na 95% CI of na nd na OR Quart2 na nd na OR Quart 3 6.5 nd 3.7 p Value 0.11 nd 0.29 95% CI of 0.65 nd 0.32 OR Quart3 65 nd 42 OR Quart 4 3.2 nd 4.9 p Value 0.33 nd 0.19 95% CI of 0.30 nd 0.46 OR Quart4 36 nd 52 Dipeptidyl peptidase IV sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 130 793 nd nd 129 1050 Average 513 1820 nd nd 486 2010 Stdev 904 3030 nd nd 840 3170 p(t-test) 8.5E−4 nd nd 4.7E−4 Min 0.924 0.651 nd nd 0.924 10.1 Max 5010 12500 nd nd 5010 12500 n (Samp) 89 18 nd nd 74 16 n (Patient) 89 18 nd nd 74 16 At Enrollment sCr or UO sCr only UO only AUC 0.67 nd 0.71 SE 0.075 nd 0.078 p 0.027 nd 0.0079 nCohort 1 89 nd 74 nCohort 2 18 nd 16 Cutoff 1 173 nd 161 Sens 1 72% nd 75% Spec 1 56% nd 57% Cutoff 2 18.2 nd 48.0 Sens 2 83% nd 81% Spec 2 22% nd 35% Cutoff 3 8.88 nd 15.1 Sens 3 94% nd 94% Spec 3 12% nd 22% Cutoff 4 457 nd 457 Sens 4 61% nd 62% Spec 4 71% nd 70% Cutoff 5 837 nd 698 Sens 5 50% nd 56% Spec 5 81% nd 81% Cutoff 6 1810 nd 1810 Sens 6 28% nd 31% Spec 6 91% nd 91% OR Quart 2 0.21 nd 0.29 p Value 0.18 nd 0.30 95% CI of 0.022 nd 0.028 OR Quart2 2.0 nd 3.0 OR Quart 3 0.96 nd 1.0 p Value 0.95 nd 1.0 95% CI of 0.21 nd 0.18 OR Quart3 4.3 nd 5.6 OR Quart 4 2.8 nd 4.1 p Value 0.14 nd 0.063 95% CI of 0.73 nd 0.93 OR Quart4 10 nd 18

TABLE 10 Comparison of marker levels in enroll EDTA samples collected from Cohort 1 (patients that did not progress beyond RIFLE stage 0 or R within 48 hrs) and in enroll EDTA samples collected from Cohort 2 (subjects reaching RIFLE stage I or F within 48 hrs). Enroll samples from patients already at stage I or F were included in Cohort 2. Beta-2-microglobulin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 2.23 3.61 2.34 4.39 2.30 3.64 Average 3.01 4.59 3.14 6.99 2.96 4.13 Stdev 2.15 4.09 2.26 6.39 2.14 2.79 p(t-test) 0.0018 2.7E−5 0.014 Min 0.824 1.38 0.824 2.19 0.824 1.38 Max 13.8 22.7 13.8 22.7 13.8 11.3 n (Samp) 139 36 165 9 110 31 n (Patient) 139 36 165 9 110 31 At Enrollment sCr or UO sCr only UO only AUC 0.64 0.79 0.64 SE 0.054 0.092 0.059 p 0.0077 0.0017 0.020 nCohort 1 139 165 110 nCohort 2 36 9 31 Cutoff 1 2.19 3.52 2.19 Sens 1 72% 78% 71% Spec 1 49% 71% 47% Cutoff 2 1.81 2.23 1.76 Sens 2 81% 89% 81% Spec 2 31% 48% 28% Cutoff 3 1.51 2.18 1.50 Sens 3 94% 100%  94% Spec 3 21% 46% 22% Cutoff 4 3.15 3.48 3.00 Sens 4 53% 78% 55% Spec 4 71% 70% 70% Cutoff 5 4.30 4.41 4.15 Sens 5 36% 44% 39% Spec 5 81% 80% 80% Cutoff 6 5.95 6.04 5.49 Sens 6 22% 44% 26% Spec 6 91% 91% 90% OR Quart 2 1.2 >2.0 0.81 p Value 0.80 <0.56 0.74 95% CI of 0.36 >0.18 0.22 OR Quart2 3.8 na 2.9 OR Quart 3 1.6 >1.0 1.2 p Value 0.42 <0.99 0.76 95% CI of 0.51 >0.062 0.36 OR Quart3 4.9 na 4.0 OR Quart 4 2.9 >6.8 2.7 p Value 0.053 <0.082 0.076 95% CI of 0.99 >0.78 0.90 OR Quart4 8.4 na 8.3 Renin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 3930 3630 nd nd 4300 3630 Average 4190 5880 nd nd 4310 5880 Stdev 1810 6690 nd nd 1930 6690 p(t-test) 0.15 nd nd 0.22 Min 1840 2100 nd nd 1840 2100 Max 10400 23300 nd nd 10400 23300 n (Samp) 43 9 nd nd 36 9 n (Patient) 43 9 nd nd 36 9 At Enrollment sCr or UO sCr only UO only AUC 0.50 nd 0.48 SE 0.11 nd 0.11 p 0.99 nd 0.89 nCohort 1 43 nd 36 nCohort 2 9 nd 9 Cutoff 1 2560 nd 2560 Sens 1 78% nd 78% Spec 1 23% nd 25% Cutoff 2 2110 nd 2110 Sens 2 89% nd 89% Spec 2  9% nd 11% Cutoff 3 2100 nd 2100 Sens 3 100%  nd 100%  Spec 3  7% nd  8% Cutoff 4 4690 nd 4900 Sens 4 22% nd 22% Spec 4 72% nd 72% Cutoff 5 5340 nd 5550 Sens 5 22% nd 22% Spec 5 81% nd 81% Cutoff 6 6480 nd 6490 Sens 6 11% nd 11% Spec 6 91% nd 92% OR Quart 2 1.0 nd 1.1 p Value 1.0 nd 0.92 95% CI of 0.12 nd 0.13 OR Quart2 8.4 nd 9.6 OR Quart 3 1.0 nd 1.9 p Value 1.0 nd 0.54 95% CI of 0.12 nd 0.25 OR Quart3 8.4 nd 14 OR Quart 4 1.6 nd 1.1 p Value 0.62 nd 0.92 95% CI of 0.23 nd 0.13 OR Quart4 12 nd 9.6 Neprilysin sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 0.607 0.869 nd nd 0.605 0.869 Average 0.878 1.43 nd nd 0.862 1.43 Stdev 0.838 1.32 nd nd 0.864 1.32 p(t-test) 0.12 nd nd 0.12 Min 0.0682 0.312 nd nd 0.0682 0.312 Max 3.76 4.43 nd nd 3.76 4.43 n (Samp) 42 9 nd nd 36 9 n (Patient) 42 9 nd nd 36 9 At Enrollment sCr or UO sCr only UO only AUC 0.66 nd 0.68 SE 0.11 nd 0.11 p 0.14 nd 0.095 nCohort 1 42 nd 36 nCohort 2 9 nd 9 Cutoff 1 0.685 nd 0.684 Sens 1 78% nd 78% Spec 1 69% nd 72% Cutoff 2 0.337 nd 0.337 Sens 2 89% nd 89% Spec 2 10% nd  8% Cutoff 3 0.308 nd 0.308 Sens 3 100%  nd 100%  Spec 3  5% nd  6% Cutoff 4 0.806 nd 0.684 Sens 4 67% nd 78% Spec 4 71% nd 72% Cutoff 5 0.992 nd 0.821 Sens 5 33% nd 67% Spec 5 81% nd 81% Cutoff 6 1.84 nd 1.84 Sens 6 33% nd 33% Spec 6 90% nd 92% OR Quart 2 0 nd 0 p Value na nd na 95% CI of na nd na OR Quart2 na nd na OR Quart 3 2.2 nd 1.0 p Value 0.42 nd 1.0 95% CI of 0.33 nd 0.11 OR Quart3 15 nd 8.7 OR Quart 4 1.5 nd 3.2 p Value 0.69 nd 0.23 95% CI of 0.20 nd 0.47 OR Quart4 11 nd 22 Carbonic anhydrase IX sCr or UO sCr only UO only Cohort 1 Cohort 2 Cohort 1 Cohort 2 Cohort 1 Cohort 2 Median 0.116 0.113 nd nd 0.122 0.113 Average 0.145 0.340 nd nd 0.150 0.340 Stdev 0.132 0.598 nd nd 0.138 0.598 p(t-test) 0.053 nd nd 0.083 Min 0.0202 0.0472 nd nd 0.0202 0.0472 Max 0.657 1.90 nd nd 0.657 1.90 n (Samp) 43 9 nd nd 36 9 n (Patient) 43 9 nd nd 36 9 At Enrollment sCr or UO sCr only UO only AUC 0.51 nd 0.49 SE 0.11 nd 0.11 p 0.95 nd 0.95 nCohort 1 43 nd 36 nCohort 2 9 nd 9 Cutoff 1 0.0653 nd 0.0579 Sens 1 78% nd 78% Spec 1 21% nd 19% Cutoff 2 0.0472 nd 0.0472 Sens 2 89% nd 89% Spec 2 14% nd 14% Cutoff 3 0.0467 nd 0.0467 Sens 3 100%  nd 100%  Spec 3 14% nd 14% Cutoff 4 0.147 nd 0.155 Sens 4 33% nd 33% Spec 4 72% nd 72% Cutoff 5 0.183 nd 0.183 Sens 5 33% nd 33% Spec 5 81% nd 81% Cutoff 6 0.241 nd 0.241 Sens 6 33% nd 33% Spec 6 91% nd 92% OR Quart 2 0.61 nd 0.30 p Value 0.62 nd 0.33 95% CI of 0.083 nd 0.026 OR Quart2 4.4 nd 3.4 OR Quart 3 0.28 nd 0.67 p Value 0.30 nd 0.69 95% CI of 0.025 nd 0.089 OR Quart3 3.1 nd 5.0 OR Quart 4 1.0 nd 1.1 p Value 1.0 nd 0.90 95% CI of 0.16 nd 0.17 OR Quart4 6.2 nd 7.2

While the invention has been described and exemplified in sufficient detail for those skilled in this art to make and use it, various alternatives, modifications, and improvements should be apparent without departing from the spirit and scope of the invention. The examples provided herein are representative of preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention. Modifications therein and other uses will occur to those skilled in the art. These modifications are encompassed within the spirit of the invention and are defined by the scope of the claims.

It will be readily apparent to a person skilled in the art that varying substitutions and modifications may be made to the invention disclosed herein without departing from the scope and spirit of the invention.

All patents and publications mentioned in the specification are indicative of the levels of those of ordinary skill in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.

The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein. Thus, for example, in each instance herein any of the terms “comprising”, “consisting essentially of” and “consisting of” may be replaced with either of the other two terms. The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention that in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be understood that although the present invention has been specifically disclosed by preferred embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art, and that such modifications and variations are considered to be within the scope of this invention as defined by the appended claims.

Other embodiments are set forth within the following claims. 

We claim:
 1. A method for evaluating and treating renal status in a subject, comprising: obtaining a body fluid sample from a subject selected for evaluation based on a determination that the subject is at risk of a future or current acute renal injury; performing an analyte binding assay configured to detect C-X-C motif chemokine 2 by introducing the body fluid sample obtained from the subject into an assay instrument which (i) contacts all or a portion of the body fluid sample with a specific binding reagent which specifically binds C-X-C motif chemokine 2, and (ii) generates an assay result indicative of binding of C-X-C motif chemokine 2 to the specific binding reagent; displaying the assay result generated by the assay instrument in a human-readable form; and correlating the assay result to the renal status of the subject by assigning the subject to a predetermined subpopulation of individuals having a known predisposition of a future acute renal injury, the assignment made by comparing the assay result or a value derived therefrom to a threshold value obtained from a population study, wherein the threshold separates the population into a first subpopulation above the threshold which is at an increased predisposition for future acute renal injury meeting the definition of RIFLE I or F within 48 hours of the time the body fluid sample is obtained relative to a second subpopulation below the threshold; and treating the subject based on the predetermined subpopulation of individuals to which the subject is assigned, wherein when the assay result or value derived therefrom is above the threshold value, the subject is treated by one or more of initiating renal replacement therapy, withdrawing delivery of compounds that are known to be damaging to the kidney, delaying or avoiding procedures that are known to be damaging to the kidney, and modifying diuretic administration.
 2. A method according to claim 1, wherein a plurality of assay results for a plurality of biomarkers, one of which plurality of assay results is the assay result indicative of binding of C-X-C motif chemokine 2 to the specific binding reagent, are combined using a function that converts the plurality of assay results into a single composite result, and the assay results displayed in human readable form comprise the single composite result.
 3. A method according to claim 1, wherein the subject is selected for evaluation of renal status based on the pre-existence in the subject of one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF.
 4. A method according to claim 1, wherein the subject is selected for evaluation of renal status based on an existing diagnosis of one or more of congestive heart failure, preeclampsia, eclampsia, diabetes mellitus, hypertension, coronary artery disease, proteinuria, renal insufficiency, glomerular filtration below the normal range, cirrhosis, serum creatinine above the normal range, sepsis, injury to renal function, reduced renal function, or ARF, or based on undergoing or having undergone major vascular surgery, coronary artery bypass, or other cardiac surgery, or based on exposure to NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin.
 5. A method according to claim 1, wherein the threshold separates the population into a first subpopulation above the threshold which is at an increased predisposition for future acute renal injury meeting the definition of RIFLE I or F within 24hours of the time the body fluid sample is obtained relative to a second subpopulation below the threshold. 